Include what the error was with the url within the bad_urls list

[thequbit]

It would be great to record why a link was marked as 'bad' within the _data['bad_urls'] list. This would make each entry in the list a dict of 'url' and 'error' rather than just a string.

There is at least one location, I think two places that _data['bad_urls'] is used. Will need to itterate through with some different code rather than just using "url in bad urls".