Update all of the gems so that Rails 4 works

- I've probably missed some, but there'll be further updates as I go
  through every error that now exists.
- Updating RSpec to 3.0.1 removes `its` - luckily there's an rspec-its
  gem that ports the 2.x behaviour to 3.
Fix some errors that came before any red tests

- Not entirely sure what these change, but I've done what the error
  output told me to do to fix the error:

  - Eager load the application only in production.
  - Remove the mass-assignment protection and the whitelist attributes
    ActiveRecord setting - this is done by strong_parameters in Rails 4.
Using match for routes is deprecated - use get for the error pages
Make RSpec render_views work again by including a new config line