Use libdefs for fbjs instead of types from node_modules

Summary:
When code depends on a module from fbjs, its types come from the node_modules
directory. This is problematic when Flow is deployed, since we can't codemod the
parts that come from node_modules.

Reviewed By: dsainati1

Differential Revision: D15547035

fbshipit-source-id: 8794a32e0f5786bcdd80eab98344d4bc623fb674

Libraries/Sample/Sample.android.js

@@ -16,6 +16,7 @@ const warning = require('fbjs/lib/warning');
 
 const Sample = {
   test: function() {
+    // $FlowFixMe warning expects a condition
     warning('Not yet implemented for Android.');
   },
 };