Merge branch 'refactor/githost'

app/models/key.rb

app/models/protected_branch.rb

app/models/users_project.rb

app/observers/key_observer.rb

app/roles/git_host.rb

app/roles/git_merge.rb

app/roles/repository.rb

app/roles/ssh_key.rb

config/environment.rb

config/initializers/5_backend.rb

features/support/env.rb

lib/gitlab/backend/gitolite.rb

lib/gitlab/backend/grack_auth.rb

lib/gitlab/git_host.rb

lib/tasks/gitlab/enable_automerge.rake

lib/tasks/gitlab/gitolite_rebuild.rake

spec/observers/key_observer_spec.rb

spec/spec_helper.rb

spec/support/gitolite_stub.rb

spec/support/monkeypatch.rb