Readd Package abstract class that was removed in #96

Specifically commit c99c63b

Previously Rpm < Package < LinuxAdmin, and LinuxAdmin is where
the .run method comes from.  By removing Package, Rpm broke
by not having access to .run.  This readds the class to fix
that issue.
Merge pull request #104 from Fryguy/readd_package_class

Readd Package abstract class that was removed in #96