v5.1.0

• add only_on_hitobjs parameter to cg.snaps (defaults to True) which, if set, only returns snaps that occur on hitobjects
• all hitobjects returned by Circleguard methods (from cg.snaps and cg.hits, for instance) are now converted to their hard_rock form if the replay had HR enabled
• add convenience method cg.beatmap(replay) which returns the beatmap associated with the given replay
• expose hitobject classes in __init__.py