* added get user by username endpoint
* added get user by username unit test and driver
* changed username length to 22 characters max
* changed Params to UserName to Username
* reorganized get user by username and get user by email formatting in model/client4
* Implement GET /channels/{channel_id}/members
* Implement GET /channels/{channel_id}/members/{user_id} endpoint for APIv4
* Implement /users/{user_id}/teams/{team_id}/channels/members endpoint for APIv4
* Fix unit test
* Implement GET /teams/{team_id} endpoint for APIv4
* Implement GET /users/{user_id}/teams endpoint for APIv4
* Implement GET /teams/{team_id}/members/{user_id} endpoint for APIv4
* added get user by email endpoint for APIv4
* added get user by email endpoint unit test and driver
* removed the appended return of user ids on logout
* Added RequireEmail to validate user email. Also updated the get user by email endpoint and unit test
