What can bookwyrm do?

As in the first alpha, bookwyrm will query Library Genesis with whatever
is passed with the --title flag and print whatever info she finds -- but
now she prints _all_ results.

However, she now also extracts URIs for mirrors. As of this release,
she can extract for golibgen (at the cost of one request) and for the
item's torrent (free). The torrent file is converted into a magnet link,
since we only want her to create files for items she is downloading.

Aside from that, the codebase has been refactored some for a more
general structure, and a bug where the item edition couldn't be
extracted has been fixed.