Adding index, show, edit views to Bug and User

Learned a couple things:
- :constraints => { :id => /[^\/]*/ }
  http://coding-journal.com/rails-3-routing-parameters-with-dots/
- def to_param to override :id as parameter
  http://railscasts.com/episodes/63-model-name-in-url
- raise 404 exception in controller
  http://stackoverflow.com/questions/2385799/how-to-redirect-to-a-404-in-rails
- collection_select and select for forms
  http://api.rubyonrails.org/classes/ActionView/Helpers/FormOptionsHelper.html#M001593