add failing test
Catch an error when parsing the URL and log it, don't throw

This catches if someone does 'jquery:foo.js' (old behaviour) when they
should now do 'jquery::foo.js'. Previously this would throw error but
now it just logs to the screen and doesn't throw.
Merge pull request #54 from jackfranklin/depreciation

Show error if one colon is used (Fixes #33)