* Listings creation and update API
- new listings controller
- refactored code to share core functionnality between api and web controllers
- code in common in classified listing concerns
- added tests for index/create/update
- json output as views
- updated a factory
* Listings creation and update API: code update
- refactored json calls
- added test cases
- added pagination for list of listings
- refactored jbuilder files
- typos
* Listings creation and update API: code update
- tags and tag_list in controller
- changed view to display both
- refactored and added test
* Listings creation and update API: code update
- small change to resolve conflit
* Listings creation and update API: code update
- added test case
- deleted unneeded test case
* Fix webhook API and add POST /api/webhooks docs
* Document GET /api/webhooks/:id
* Fix DELETE /api/webhooks/{id} and document it
* Add proper 404 specs
