Merge pull request #91 from aCarpenter/master

[ISSUE-82]: Send user email when bounty is rejected by all candidate artists; add rubocop to check code style
Admins may edit bounties and delete comments.
Lock rspec at version 2.99 until we adapt to the breaking changes in rspec 3.
Use .present? instead of == nil to make a nil check more Rails idiomatic.
Add request specs ensuring that unauthorized users can't access the Bounty#edit action.
Move SessionsHelper methods into ApplicationController instead.

The SessionsHelper methods provided access to the user model for the
logged-in user and was used so extensively in controllers that all of
them imported SessionsHelper. With such extensive use of these helper
methods in controller logic, it made sense to move them into
ApplicationController. Also, this allows them to be easily stubbed
during tests, while the helper methods were virtually impossible to
stub.
Add a comment on an extra gem to install when upgrading to Rspec 3.
Update gems to latest versions.