Remove reference to therubyracer from README.md 

therubyracer doesn't currently work to build ember.js, and this patch removes an instruction to use it.
Use ENV var to disable version logging of used libraries
Merge pull request #2090 from regularfry/master

Patch to avoid bumping into issue #2069
object proxy defines properties that are passed to create that do not exist in the prototype
expose RSVP on the ember namespace
Merge pull request #2162 from stefanpenner/master

Expose RSVP on the Ember namespace
Merge pull request #2155 from javierav/debug

Use ENV var to disable version logging of used libraries