Rename Jira API to Jira client

The backing jira-ruby library refers to the object that makes REST calls
as the client, not the API. This commit renames all references to the
Jira API to `client` so that we're consistent about naming.
Merge branch 'rename-jira-client'
Extract shared delayed job behavior to a mixin
Merge branch 'refactor-delayed-job'
Update Jira specs for api -> client rename
Fix missed instance of jira api -> client
Extract pull request app travis and travis auth
Clean up pull request app requires
Add specs for github controller
Add preliminary support for tunable event outputs
Add specs for github pull request controller
Remove formatting tests from '/github/event' route

The exact implementation of github events is controlled by the
controller class that was instantiated, but the test coverage was in the
route specs. Since test coverage has been added for the pull request
controllers, these tests are no longer needed.
Merge branch 'tunable-event-outputs'