Filter team members by role (#491)

* Team: support filtering members by role

* Team: support adding membership with role

github/Team.py

@@ -228,16 +228,22 @@ class Team(github.GithubObject.CompletableGithubObject):
         )
         self._useAttributes(data)
 
-    def get_members(self):
+    def get_members(self, role=github.GithubObject.NotSet):
         """
-        :calls: `GET /teams/:id/members <http://developer.github.com/v3/orgs/teams>`_
+        :calls: `GET /teams/:id/members <https://developer.github.com/v3/teams/members/#list-team-members>`_
+        :param role: string
         :rtype: :class:`github.PaginatedList.PaginatedList` of :class:`github.NamedUser.NamedUser`
         """
+        assert role is github.GithubObject.NotSet or isinstance(role, (str, unicode)), role
+        url_parameters = dict()
+        if role is not github.GithubObject.NotSet:
+            assert role in ['member', 'maintainer', 'all']
+            url_parameters["role"] = role
         return github.PaginatedList.PaginatedList(
             github.NamedUser.NamedUser,
             self._requester,
             self.url + "/members",
-            None
+            url_parameters
         )
 
     def get_repos(self):