Merge remote-tracking branch 'ce/master' into merge_ce

Conflicts:
	README.md
	app/assets/javascripts/project.js.coffee
	app/models/concerns/mentionable.rb
	app/models/project.rb
	app/models/project_services/jira_service.rb
	app/models/service.rb
	app/models/user.rb
	app/services/git_push_service.rb
	config/initializers/1_settings.rb
	config/routes.rb
	db/schema.rb
	doc/integration/README.md
	doc/integration/external-issue-tracker.md
	doc/integration/github.md
	spec/controllers/import/github_controller_spec.rb
	spec/helpers/merge_requests_helper.rb
	spec/lib/gitlab/upgrader_spec.rb
	spec/models/note_spec.rb
	spec/requests/api/groups_spec.rb
	spec/services/git_push_service_spec.rb