Refactor controllers to be more readable.

PasswordsController has been left out, because it's behavior is to
be changed to not report any failure when an account can't be found.
CHANGELOG [ci skip]
Merge pull request #20 from ysbaddaden/refactor-controllers

Refactor controllers
CodeClimate test coverage
Merge remote-tracking branch 'origin/master'
Fix: outdated Gemfile.lock
Update Gemfile dependencies
Rails 4.2 compatibility
depending on bcrypt gem (not bcrypt-ruby)
Now testing on Rails master, 4.2.x, 4.1.x and 3.2.x
Travis configuration upgrade