Only update Agent's last_event_at on Event creation, not when Events are updated.
reload to be clear
Merge remote-tracking branch 'origin/master' into event_update_should_not_touch_last_event_at

Conflicts:
	app/models/event.rb
Merge pull request #481 from cantino/event_update_should_not_touch_last_event_at

Only update Agent's last_event_at on Event creation, not when Events are updated.