Do not depend on `package-menu-*`

This commit removes the need for using the package menu explicitly,
since the package menu is a user front-end, it is more prone to changes.

The main idea is due to this [issue](https://github.com/purcell/emacs.d/issues/33).
Stub a single package into the update test.
Install directly from archive.
Merge pull request #12 from rranelli/do-not-use-package-menu-functions

Do not use package menu functions