Fix expiration of member data

* The `expire_leaderboard` and `expire_leaderboard_at` methods should also set expiration on the member data hash to not retain information.
Bump version
Added  functionality
Removed `remove_members_in_rank_range` because the Redis method is not
actually deleting by rank, but by index. Silly me for forgetting that
little fact.
Remove method from README
Merge pull request #34 from agoragames/version-3.0.2

Version 3.0.2