Adding user_teams api

GITLAB-698 (GITLAB-116)
Add user_team api

GITLAB-698 (GITLAB-116)
Fixed an issue with access level var in add team project

GITLAB-698 (GITLAB-116)
Fixed a broken test
Made 409's throw exceptions

-Added more detail to error messages

GITLAB-721 (GITLAB-116)
Merge pull request #11 from karlhungus/feature-user-teams-api

Feature user teams api