[Docs] Suggest installing npm 2 instead of npm 3 for perf reasons

npm 3 is really slow compared to npm 2, to the extent that people are reporting bugs.

docs/EmbeddedAppIOS.md

@@ -14,6 +14,7 @@ Since React makes no assumptions about the rest of your technology stack – it
 - [CocoaPods](http://cocoapods.org/) – `gem install cocoapods`
 - [Node.js](http://nodejs.org)
   - Install **nvm** with [its setup instructions here](https://github.com/creationix/nvm#installation). Then run `nvm install node && nvm alias default node`, which installs the latest version of Node.js and sets up your terminal so you can run it by typing `node`.  With nvm you can install multiple versions of Node.js and easily switch between them.
+  - If you are using Node 5.0 or newer, we recommend installing npm 2, which is much faster than npm 3. After installing Node, run `npm install -g npm@2`
 - Install your copy of React Native under your `node_modules` directory where your JS resides.
 
 ## Install React Native Using CocoaPods

docs/GettingStarted.md

@@ -13,6 +13,7 @@ next: android-setup
 2. [Homebrew](http://brew.sh/) is the recommended way to install Watchman and Flow.
 3. Install [Node.js](https://nodejs.org/) 4.0 or newer.
   - Install **nvm** with [its setup instructions here](https://github.com/creationix/nvm#installation). Then run `nvm install node && nvm alias default node`, which installs the latest version of Node.js and sets up your terminal so you can run it by typing `node`. With nvm you can install multiple versions of Node.js and easily switch between them.
+  - If you are using Node 5.0 or newer, we recommend installing npm 2, which is much faster than npm 3. After installing Node, run `npm install -g npm@2`.
   - New to [npm](https://docs.npmjs.com/)?
 4. `brew install watchman`. We recommend installing [watchman](https://facebook.github.io/watchman/docs/install.html), otherwise you might hit a node file watching bug.
 5. `brew install flow`, if you want to use [flow](http://www.flowtype.org).