* Update yum_repository.py
Having spent some time trying and googling how to enable an installed repo with this, I discovered that the thread at https://github.com/ansible/ansible-modules-extras/issues/2384 had decided that this would not be supported and recommended use of ini_file instead. Since I am sure I'm not alone in expecting yum-repository to support enabling/disabling a configured repo, I suggest adding a note so people find this easier.