Corrected maxResults limit for GetAllRooms()

Modified to reflect information from HipChat API docs (see
https://www.hipchat.com/docs/apiv2/method/get_all_rooms)
Added support for include-private parameter to GetAllRooms()

Added missing flag to match HipChat API documentation (see
https://www.hipchat.com/docs/apiv2/method/get_all_rooms)
Merge pull request #10 from Jonax/master

Modifications to GetAllRooms() as per HipChat docs for v2/rooms