Introduce Support for Ubuntu 16.04

[gmolto]

Hi,

We where doing some tests to deploy a Mesos cluster on AWS, which uses this role but the deployment fails with the following error:

TASK [indigo-dc.docker : Fail if OS distro is not Ubuntu 14.04] ****************
fatal: [34.198.199.10_22]: FAILED! => {"changed": false, "failed": true, "msg": "The role is designed only for Ubuntu 14.04"}

Can we have support for Ubuntu 16.04 for this role.

Thank you very much in advance.

[maricaantonacci]

Sure. The support will be added soon.

[maricaantonacci]

Merged #6