Remove group :assets for Rails 4.
Merge pull request #772 from brianvanburken/gemfile_fix

Fix gemfile for Rails 4 assets.
Just leave github issue tracker as default
Remove allow_comments_with_issue_tracker config
Merge pull request #775 from errbit/remove_allow_comments_with_issue_tracker

Remove allow_comments_with_issue_tracker config
Merge pull request #773 from errbit/remove_other_issue_trackers

Just leave github issue tracker as default
Replace issue creation interactor with Issue model
Dont use fake issue tracker from errbit_plugin gem

Fake issue tracker is a mock tracker for tests only, it should live in errbit core
Replace issue creation interactor spec with issue_spec
Issue has_one issue_tracker
Issue tracker model should not have any view/render concerns
Fix problem_controller and spec
Fix tests
Fix more tests