Support the Ubuntu 14.04 release

As seen with Feanil, this switches the support from Ubuntu 12.04 to Ubuntu 14.04.

There might be an issue with MITx 6.341x course but I can't pull the course so
I'm not able to test it.
In order to not forget about this course, I've left the ansible commands that
where necessary on Ubuntu 12.04.

Let me know if I can do something else for this PR.