Remove knowledge of fbjs from the packager

Summary:Follow-up to https://github.com/facebook/react-native/pull/5084

This…
- changes all requires within RN to `require('fbjs/lib/…')`
- updates `.flowconfig`
- updates `packager/blacklist.js`
- adapts tests
- removes things from `Libraries/vendor/{core,emitter}` that are also in fbjs
- removes knowledge of `fbjs` from the packager

Closes https://github.com/facebook/react-native/pull/5084

Reviewed By: bestander

Differential Revision: D2926835

fb-gh-sync-id: 2095e22b2f38e032599d1f2601722b3560e8b6e9
shipit-source-id: 2095e22b2f38e032599d1f2601722b3560e8b6e9

Libraries/ReactIOS/requireNativeComponent.js

@@ -24,7 +24,7 @@ var processColor = require('processColor');
 var resolveAssetSource = require('resolveAssetSource');
 var sizesDiffer = require('sizesDiffer');
 var verifyPropTypes = require('verifyPropTypes');
-var warning = require('warning');
+var warning = require('fbjs/lib/warning');
 
 /**
  * Used to create React components that directly wrap native component