[Managing User sign in]

 - New button Manage Users in notifications#index
 - Spec request, registered users can see Manage Users and invited users can't see it.
[Managing User sign in]

 - Notification#index, manage users link corrected.
[Managing User sign in]

 - factory user and spec request fixed.
Merge pull request #29 from insignia4u/managin-user-sign-in

[Managing User sign in]