Add upgrade documentation for Ubuntu 14.04 from Ubuntu 12.04
Revert "Make changes to CentOS SSL certificate guide and rename for CentOS 6&7"

This reverts commit 16e90eb9f9f34415c4cc7e0af6e58bccbfaa329d.
Added note on root SSH login.
Merge pull request #2 from thetechstewart/ubuntu1204to1404

Added note on root SSH login.
Merge pull request #103 from drussell393/ubuntu1204to1404

Add upgrade documentation for Ubuntu 14.04 from Ubuntu 12.04