Have Eventbrite_Query use the "event_details" endpoint for queries using the "p" parameter.
Add a filter on get_post_metadata so that has_post_thumbnail() returns correctly for events.
Merge branch 'master' into get-event
Improve eventbrite_get_event() as a helper function by using the event_details endpoint. Then mop up the devastation.

With the addition of the event_details endpoint, it makes sense that any requests for individual events go through it. This didn't sit well with the Eventbrite_Query and Eventbrite_Post classes, which were relying on eventbrite_get_event() for processing results to queries of multiple events. Eventbrite_Query now relies on its create_eventbrite_event() method for determining if Eventbrite_Post::get_instance() is really needed (get_instance() continues to use the eventbrite_get_event() helper function).

This commit also renames the Eventbrite_Post class to Eventbrite_Event, because Eventbrite_Post was just silly, and modelling that closely to WP_Post simply isn't justified.
Ensure IDs passed to the request method are positive, non-zero integers.
Validate the ID passed in before bothering to make an API request.
Correct references of Eventbrite_Post to Eventbrite_Event.
Corrections and improvements to docblocks and inline comments.