WIP: URL blacklisting

So, this is what I mentioned on #403. Or at least a start on it. :grin:

I not even test it yet, I'm not in my better conditions now (Windows here :cry:), maybe soon I'll add some specs and really test if it works.

But for instance, if you have some kind of comments about this changes, feel free! You already are!
Now it is used. :grin: