Rename method.
Members are now added to the group (and removed before saving).
Add a test for retrieval of a group with a member.
Added function addMembersToGroup + tests.
Refactored groupsAndMembers: Now we can add the members to a group.
Now the groups show their member count in the overview page.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	lib/groups/index.js
Merge pull request #201 from NicoleRauch/master

Die Gruppenübersicht zeigt jetzt die Mitgliederzahl der Gruppe