[JRO] Use pry-rails

This replaces irb for the console. Much better.
[JRO] Remove User feature envy out of Messageboard

Messageboard had had an active_users instance method that did
most of its work inside the user object. Problem 1 - it was a
sql query. Problem 2 - it should be in the User class instead.

* Move method to User
* Add test coverage
* Change to use AR instead of sql
* Clean up user_spec
* Update call to method in the view
[JRO] Clean up role spec & factories a bit