Older git archive commands create tar archives even with a tar.gz
extension. So change it to always create tar archives and have
the install_role method cope.
Removed ssh roles from the test case as they don't work unless
you can connect to bitbucket via ssh and have your key there.
Corrected a minor typo in error messages
* Roles can now be given a friendly name as third field in role spec csv
* Roles can be installed from URL (not just from archived SCMs)
* Integration tests to demonstrate this
* Unit tests to ensure that role spec parsing works as expected
