Fix rspec-puppet dependency on rspec < 3.0.0

The tests was failing because rspec puppet need
rspec < 3.0.0.

This commit fix this dependency on Gemfile.
change fixtures module stdlib to use https instead of git

Make stdlib fixture use https instead of git.

It works on more strict networks.
Merge pull request #10 from lmello/fix_spec_dependency

Fix spec dependency