Add basic support for Coveralls reports

Note:

  - Requires the 'coveralls' gem
  - Reports lines that have created a resource that has been asserted

This might look a bit weird in coveralls, because this is not what is usually reported by coverage, but I'm just building on top of what coverage support in rspec-puppet currently does, which is reporting resources that were declared but not tested (vs resources that were never declared when parsing the code, which is what is traditionally done).

An example of coveralls output can be found at https://coveralls.io/r/raphink/puppet-lvm