[io.js] Print a warning message if the user is not on io.js 2.x

Summary:
Detects if the user is on Node or io.js 1.x and prints a banner explaining how to upgrade. We probably should link to more detailed upgrade docs so this is just a start.

I also added a function to format banners that is kind of useful.

Addresses part of #1737

![packager-banner](https://cloud.githubusercontent.com/assets/379606/8447050/ad615402-1f67-11e5-8c02-ece5f7488135.png)

Closes https://github.com/facebook/react-native/pull/1824
Github Author: James Ide <ide@jameside.com>

checkNodeVersion.js

@@ -0,0 +1,40 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+var chalk = require('chalk');
+var semver = require('semver');
+
+var formatBanner = require('./formatBanner');
+
+function checkNodeVersion() {
+  if (!semver.satisfies(process.version, '>=2.0.0')) {
+    var engine = semver.lt(process.version, '1.0.0') ? 'Node' : 'io.js';
+    var message = 'You are currently running ' + engine + ' ' +
+      process.version + '.\n' +
+      '\n' +
+      'React Native is moving to io.js 2.x. There are several ways to upgrade' +
+      'to io.js depending on your preference.\n' +
+      '\n' +
+      'nvm:       nvm install iojs && nvm alias default iojs\n' +
+      'Homebrew:  brew unlink node; brew install iojs && brew ln iojs --force\n' +
+      'Installer: download the Mac .pkg from https://iojs.org/\n' +
+      '\n' +
+      'About io.js:     https://iojs.org\n' +
+      'Follow along at: https://github.com/facebook/react-native/issues/1737';
+    console.log(formatBanner(message, {
+      chalkFunction: chalk.green,
+      marginLeft: 1,
+      marginRight: 1,
+      paddingBottom: 1,
+    }));
+  }
+}
+
+module.exports = checkNodeVersion;

formatBanner.js

@@ -0,0 +1,108 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+var _ = require('underscore');
+var wordwrap = require('wordwrap');
+
+var HORIZONTAL_LINE = '\u2500';
+var VERTICAL_LINE = '\u2502';
+var TOP_LEFT = '\u250c';
+var TOP_RIGHT = '\u2510';
+var BOTTOM_LEFT = '\u2514';
+var BOTTOM_RIGHT = '\u2518';
+
+/**
+ * Prints a banner with a border around it containing the given message. The
+ * following options are supported:
+ *
+ * type Options = {
+ *   // A function to apply to each line of text to decorate it
+ *   chalkFunction: (string: message) => string;
+ *   // The total width (max line length) of the banner, including margin and
+ *   // padding (default = 80)
+ *   width: number;
+ *   // How much leading space to prepend to each line (default = 0)
+ *   marginLeft: number;
+ *   // How much trailing space to append to each line (default = 0)
+ *   marginRight: number;
+ *   // Space between the top banner border and the text (default = 0)
+ *   paddingTop: number;
+ *   // Space between the bottom banner border and the text (default = 0)
+ *   paddingBottom: number;
+ *   // Space between the left banner border and the text (default = 2)
+ *   paddingLeft: number;
+ *   // Space between the right banner border and the text (default = 2)
+ *   paddingRight: number;
+ * };
+ */
+function formatBanner(message, options) {
+  options = options || {};
+  _.defaults(options, {
+    chalkFunction: _.identity,
+    width: 80,
+    marginLeft: 0,
+    marginRight: 0,
+    paddingTop: 0,
+    paddingBottom: 0,
+    paddingLeft: 2,
+    paddingRight: 2,
+  });
+
+  var width = options.width;
+  var marginLeft = options.marginLeft;
+  var marginRight = options.marginRight;
+  var paddingTop = options.paddingTop;
+  var paddingBottom = options.paddingBottom;
+  var paddingLeft = options.paddingLeft;
+  var paddingRight = options.paddingRight;
+
+  var horizSpacing = marginLeft + paddingLeft + paddingRight + marginRight;
+  // 2 for the banner borders
+  var maxLineWidth = width - horizSpacing - 2;
+  var wrap = wordwrap(maxLineWidth);
+  var body = wrap(message);
+
+  var left = spaces(marginLeft) + VERTICAL_LINE + spaces(paddingLeft);
+  var right = spaces(paddingRight) + VERTICAL_LINE + spaces(marginRight);
+  var bodyLines = _.flatten([
+    arrayOf('', paddingTop),
+    body.split('\n'),
+    arrayOf('', paddingBottom),
+  ]).map(function(line) {
+    var padding = spaces(Math.max(0, maxLineWidth - line.length));
+    return left + options.chalkFunction(line) + padding + right;
+  });
+
+  var horizontalBorderLine = repeatString(
+    HORIZONTAL_LINE,
+    width - marginLeft - marginRight - 2
+  );
+  var top = spaces(marginLeft) + TOP_LEFT + horizontalBorderLine + TOP_RIGHT +
+    spaces(marginRight);
+  var bottom = spaces(marginLeft) + BOTTOM_LEFT + horizontalBorderLine +
+    BOTTOM_RIGHT + spaces(marginRight);
+  return _.flatten([top, bodyLines, bottom]).join('\n');
+}
+
+function spaces(number) {
+  return repeatString(' ', number);
+}
+
+function repeatString(string, number) {
+  return new Array(number + 1).join(string);
+}
+
+function arrayOf(value, number) {
+  return _.range(number).map(function() {
+    return value;
+  });
+}
+
+module.exports = formatBanner;

package.json

@@ -23,7 +23,9 @@
     "lint": "node linter.js Examples/",
     "start": "./packager/packager.sh"
   },
-  "dependencies": {},
+  "dependencies": {
+    "wordwrap": "^1.0.0"
+  },
   "devDependencies": {
     "jest-cli": "git://github.com/facebook/jest#0.5.x",
     "eslint": "0.9.2"

packager.js

@@ -30,6 +30,8 @@ var chalk = require('chalk');
 var connect = require('connect');
 var ReactPackager = require('./react-packager');
 var blacklist = require('./blacklist.js');
+var checkNodeVersion = require('./checkNodeVersion');
+var formatBanner = require('./formatBanner');
 var launchEditor = require('./launchEditor.js');
 var parseCommandLine = require('./parseCommandLine.js');
 var webSocketProxy = require('./webSocketProxy.js');
@@ -108,16 +110,19 @@ if (options.assetRoots) {
   }
 }
 
-console.log('\n' +
+checkNodeVersion();
-' ===============================================================\n' +
+
-' |  Running packager on port ' + options.port +          '.       \n' +
+console.log(formatBanner(
-' |  Keep this packager running while developing on any JS         \n' +
+  'Running packager on port ' + options.port + '.\n'+
-' |  projects. Feel free to close this tab and run your own      \n' +
+  '\n' +
-' |  packager instance if you prefer.                              \n' +
+  'Keep this packager running while developing on any JS projects. Feel free ' +
-' |                                                              \n' +
+  'to close this tab and run your own packager instance if you prefer.\n' +
-' |     https://github.com/facebook/react-native                 \n' +
+  '\n' +
-' |                                                              \n' +
+  'https://github.com/facebook/react-native', {
-' ===============================================================\n'
+    marginLeft: 1,
+    marginRight: 1,
+    paddingBottom: 1,
+  })
 );
 
 console.log(