As you may know, the Atareao team has created an app called Power Commands, that enables the users to easily turn off, reboot, suspend, hibernate, log out and block, via the Unity Dash.
The latest version available is Power Commands 2.0, which has been recently released, bring available for Ubuntu 15.10 Wily Werewolf, Ubuntu 15.04 Vivid Vervet and Ubuntu 14.04 Trusty Tahr due to the fact that it has been created to work with systemd.
Up to date Power Commands packages are available via the Atareao PPA, so installing the software on Ubuntu 15.04 Vivid Vervet systems is easy. Just add the PPA to your system, update the local repository index and install the power-commands package:
$ sudo add-apt-repository ppa:atareao/atareao
$ sudo apt-get update
$ sudo apt-get install power-commands
Optional, to remove power-commands, do:
$ sudo apt-get remove power-commands