Serve the original version of the image if the client accepts it
Merge pull request #121 from christeredvartsen/develop

Serve the original version of the image if the client accepts it
Added an event listener that handles 304 Not Modified
Removed logic from the resource classes that handled 304 Not Modified since this has been moved to an event listener instead
Removed logic handling 304 Not Modified
Instead of sending the response this listener will now halt the application and return
Added a method that makes the response into an error. Also added tests
If the client requests a specific image type, drop the content negotiation (as in all other resources)
Changed the events the listener listens for
Added an event listener that formats the response correct according to the headers found in the request. Also added test case
Added two new listeners to the dist config
Removed some error handling code that now lives in the response implementation
If the response body has not been formatted, encode to JSON
Added comment
Changed event name
Swapped parameter order
Updated docs
Changed name of the cache adapter from Apc to APC
Use the SplPriorityQueue for events
Updated the test case