Fix up integration tests

Several improvements to integration tests:

* Syntax changes to aid reliability (e.g. adding ```casper.then``` where needed)
* Wait timeout functions with screenshots to better help diagnose failues
* Listeners for error status codes (404, 500, 504)
* Changed the archived liveblog that we test as the previous one was quite large and often returned 504 on code
* Added liveblogs back to article test command
* Fixed broken gallery test