Only one link per email to prevent clicking the wrong one.
Add short path route for groups.
Add monthly active users to the admin dashboard.
Fixes to group route tests, thanks DZ
Merge branch 'prevent-two-links-in-emails' into 'master'

Prevent-two-links-in-emails

Only one link per email to prevent clicking the wrong one.
Merge branch 'active-users' into 'master'

Active users

Show the number of active users in the dashboard.
Merge branch 'routing-for-groups' into 'master'

Routing for groups

Implements http://feedback.gitlab.com/forums/176466-general/suggestions/5723800-group-url-on-root-path-groups-name-instead-of-g