Automate rebuilding the contributor list

This extends the hacks in the Modulefile to automatically rewrite the
contributor list in a stand-alone file.  This makes it practical to give
public credit to the folks who have contributed to the module without human
error dropping some of them.

Closes #122.

Signed-off-by: Daniel Pittman <daniel@puppetlabs.com>
Merge pull request #123 from daniel-pittman/feature/master/122-automate-the-contributor-list-in-readme-md

Automate rebuilding the contributor list