From-scratch CentOS 6.5 Docker image

As-minimal-as-possible CentOS 6.5 image using febootstrap. The idea of checking in a large, opaque binary file makes me itch, but the Docker model doesn't currently allow for more control over image creation. This is hopefully the only time I'll have to do this…

Ok, this also contains the EPEL repo configs. But it's still pretty minimal.

Modeled after docker-brew-ubuntu.

generating filesystem image

./build_centos.sh