v2.7.9

1.Renamed announcement_type to type
2.Renamed challenge_type to type
3.Removed ?after|before query from GET /challenges/list
4.Added ?start_after|before and ?end_after|before to GET /challenges/list
5.Removed ?roles query from GET /members/list
6.Added ?include_roles|exclude_roles to GET /members/list
7.Added creator field to event and challenge objects
8.Fixed legacy functions using role id to order roles