Add ability to to clean up the reports directory

Defaults to removing files in Puppet's setting for reportdir at 30 days.
Travis workaround needed for testing ruby 1.8.7

https://github.com/bundler/bundler/issues/2784
Stop supporting Puppet 2.7
Merge pull request #54 from ghoneycutt/cleanup_reportdir

Add ability to to clean up the reports directory