Install Unity 8 on Ubuntu 13.10

According to Unity8Desktop wiki following the release of the Alpha version of Unity 8, the plan was to provide a preview Unity 8 on Mir session for Ubuntu 13.10 for evaluation and testing. The integration of Unity 8 into Ubuntu Desktop is not scheduled to happen for 13.10 but will only be fully integrated for 14.10 which is set to be release in April 2014. While we wait for this release, I will go ahead and install it on Ubuntu 13.