Issue #35 Require puppet-rspec version 0.1.6

In puppet-rspec versions >= 1.0.0, a parameter was added to the
catalogue method.  This broked a number of the rspec tests.  By
requiring puppet-rspec version 0.1.6 in .gemfile, you can get the tests
to pass again.
Merge pull request #35 from Element84/Issue35

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