Removed support for ruby 1.8.7 during tests.

This will remove ruby 1.8.7 from the test run, as ruby 1.8.7 no longer has support.
This fixes the broken build and returns the passing status.

If you enable the hook on https://travis-ci.org we will be able see the build results for reach pull request.

![puppet-python-build](https://travis-ci.org/daniellawrence/puppet-python.svg?branch=remove_ruby_1.8.7_support "GREEN")