Use our nifty URL detector library to check for previous import

Our `find_by_url` already checks for www and non-www, encoded and non-encoded, etc versions of the URL. Let's use it. With spec!
Merge branch 'refs/heads/master' into 0.9.13-issue-3574-wwwwww

Conflicts:
	spec/models/story_parser_spec.rb
Merge pull request #1515 from CristinaRO/0.9.13-issue-3574-wwwwww

Use our nifty URL detector library to check for previous import