Support rspec-puppet v1.0.0

include_class has been replaced with contain_class.
http://bombasticmonkey.com/2013/12/05/rspec-puppet-1.0.0/
Pin rspec-puppet to 1.x releases

Since contain_class is only in 1.x or greater, we add an explicit pin in the
Gemfile for this.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #110 from kbarber/rspec_puppet_v1

Support rspec-puppet v1.0.0