Update README about Rails versions so it doesn't keep getting out of date
Fix capitalization of RailsBridge
Remove therubyracer, I still don't know what it was for
Create and delete a temp app to pre-install more gems [fixes #8]
Don't install the protected_attributes gem

Protected attributes is for using `attr_accessible` in Rails 4.

The curriculum does not use `attr_accessible`, so we don't need to install the
gem.
Don't use forks of chruby and ruby-install

Closes #4.
Remove Python-Twisted dependencies (manually, not properly installed for autoremove)