Fix deprecated methods on rspec 2.14
Update shoulda-matchers to 2.2.0 and update specs

More information about the matchers that were replaced at:
http://robots.thoughtbot.com/post/47031676783/shoulda-matchers-2-0
Finish migrating to strong_parameters in all models

Several attr_accessible's used before are not necessary anymore. They were
there to allow the application to call update_attributes at some methods
and actions that are not triggered by the user.