Update rails upto 4.1.2

Update rails up to 4.1.2:

- Replace `RailsBase::Application` with `Rails.application`
- Extract list of precompile assets to [`config/initializers/assets.rb`](https://github.com/fs/rails-base/blob/8e2d7753635408fbbe8490d07946422d3085efb0/config/initializers/assets.rb)
- Do not dump schema.rb for staging and production envs
- Raise en error on missing translation for test env