Make bundling for deployment happy

When deploying to heroku or running on travis, I was seeing:

You are trying to install in deployment mode after changing
       your Gemfile. Run `bundle install` elsewhere and add the
       updated Gemfile.lock to version control.
       You have added to the Gemfile:
       * therubyracer (~> 0.11.3)

I assume because of the conditional we had for platform. Sooo let's take
that out.
Merge branch 'fix-ubuntu-deployment' into heroku-button