Add a yum provider

Here we add a yum provider which uses the yum python interface directly to
interact with yum.  This allows you to manage yum-based systems without needing
to install puppet.

To enable add `plugin.package.provider = yum` to your mcollective server.cfg.
Add rspec testing to the yumpackage provider

This adds basic rspec testing to the yumpackage provider.  Much of the behaviour of
the provider is implemented by the yumHelper.py, so here we check that it's
being invoked correctly.