Add the "event_details" endpoint, used to get a single event from the Eventbrite API.

The "p" query parameter is used by Eventbrite_Query to pass an event ID to the API.

http://developer.eventbrite.com/docs/event-details/
Merge branch 'master' into event-details
Remove endpoint exceptions now that the call() method accepts a third parameter for passing an event ID.
Merge pull request #5 from Automattic/event-details

Add the "event_details" endpoint, used to get a single event from the Ev...