Use a separate babel config for the local-cli and the packager

Summary:
This separates the babel config of the local-cli and the packager from the one used by the transforms of the packager since it doesn't run in the same environment and the local-cli/packager doesn't require react specific transforms and runs in node 4 so we can also avoid some es2015 transforms that node already supports.

I had to move the code in cli.js so it can still run in node 0.12 that doesn't support `const` since it is no longer transformed.

**Test plan**
Run the local-cli on node 0.12 and there should be a message saying that it requires at least node 4.
Run the local-cli on node 4 and 5 and everything should work the same as before.

I was also hoping for some perf gains but there was nothing noticeable. I did benchmark the babel-register call and it stayed pretty much the same. As for runtime performance it can help if there are optimisations for es2015 features in node.
Closes https://github.com/facebook/react-native/pull/6155

Reviewed By: bestander

Differential Revision: D3301008

Pulled By: davidaurelio

fbshipit-source-id: 504180d158a1e50bc03e28fb0d1e53d0731ce32f

babelRegisterOnly.js

@@ -12,20 +12,19 @@ Array.prototype.values || require('core-js/fn/array/values');
 Object.entries || require('core-js/fn/object/entries');
 Object.values || require('core-js/fn/object/values');
 
-var fs = require('fs');
-var path = require('path');
-
 var _only = [];
 
-function readBabelRC() {
-  var rcpath = path.join(__dirname, 'react-packager', 'rn-babelrc.json');
-  var source = fs.readFileSync(rcpath).toString();
-  return JSON.parse(source);
-}
-
 module.exports = function(onlyList) {
   _only = _only.concat(onlyList);
-  var config = readBabelRC();
-  config.only = _only;
-  require('babel-register')(config);
+
+  require('babel-register')({
+    presets: ['es2015-node'],
+    plugins: [
+      'transform-flow-strip-types',
+      'syntax-trailing-function-commas',
+      'transform-object-rest-spread',
+    ],
+    only: _only,
+    sourceMaps: 'inline',
+  });
 };

package.json

@@ -1,5 +1,5 @@
 {
-  "version": "0.3.2",
+  "version": "0.4.0",
   "name": "react-native-packager",
   "description": "Build native apps with React!",
   "repository": {