Add :build and :clean tasks to Rakefile
Test for both, Ruby 1.8.7 and 1.9.3 on Travis CI
Add ensure parameter

This requires heavy use of conditionals and the chaining syntax
(http://docs.puppetlabs.com/puppet/2.7/reference/lang_relationships.html#chaining-arrows)
in order to do things in the right order based on creation or removal,
but should be smooth.
Update docs to reflect the "ensure" parameter
Add Comment parameter
Tidy up comment stuff a bit
Give @guerremdq credit for the comment parameter
Use Rake tasks from torrancew/puppet-cron to fix #2