OpenZIS installation guide

I have spent a day or so trying to get the OpenZIS project up and running on a CentOS machine. A lack of updated instructions and an older code base made this process harder than I expected.

While I am still investigating if OpenZIS will meet my needs, I wanted to publish what I did as a reference to others who might try to install it. The doc is in my forked version of OpenZIS. Once I have tested things more, I will likely submit a pull request to the author.

https://github.com/ewannema/OpenZIS/blob/master/INSTALL_CENTOS_6.md