Don't normalize auth data in feed url

The util.normalize_feed_url method forces the entire feed url to lower case. However, if the url includes authentication data, forcing it to lowercase could invalidate it.

For example, if the url is `http://User:Password@example.com/feed`, and the remote service doing the authenticating is case sensitive the result will be a 401.

This pull request fixes that problem, and includes tests for that as well as the other examples given in the comments section of that method.