Made ChanRipper more universal.

Added a nice way to add extra chan sites. This makes sure that the files
are the correct ones (self_hosted). Generic sites still work. Check
http://www.allchans.org/ sometime. And 4chan-x for the list of archives.
The "Can't rip this url" error now gives the message.
Added ChanSite Helper class.
Updates ChanRipperTest urls.

testVineboxAlbums is still failing.