EPEL Testing documentation

[T.C. Hollingsworth]

Somebody asked me about one of my updates sitting in epel-testing
today, and I noticed that we didn't have a nice page like we do for
Fedora [1] that explains how the testing repository and bodhi, etc.
work to point them to.

So I forked the Fedora documentation and modified it to apply to EPEL instead:
https://fedoraproject.org/wiki/EPEL/testing

Hopefully others will find this useful.  If I missed anything or you
have anything useful to add, please use your wiki powers!

Thanks,
-T.C.

[1] https://fedoraproject.org/wiki/QA:Updates_Testing