Instructions for installing on fedora 20

A start on the documentation parts of: https://clusterhq.atlassian.net/browse/FLOC-970
The error appears to mean that the package was installed already.  I suggest calling out this case so that users understand the error message they get - or better yet, change these steps to not try to install a package that is already installed.  If the latter is hard, it needn't hold up this issue but please file a follow-up issue.