Update to newest epel-release for EL7

Maybe we should look into doing something like this:

- https://stackoverflow.com/questions/14016286/how-to-programmatically-install-the-latest-epel-release-rpm-without-knowing-its
- https://github.com/zigg/octothorpe/commit/c3b0cdf751a6818385925c7b358361e000076daf