Use a more robust html parser (lxml) to avoid parsing issues.

ElementTree was failing with the following message:

    xml.etree.ElementTree.ParseError: not well-formed (invalid token)

+ Refactor the code to make it more readable ^^
Use mkaurball since .AURINFO file seems mandatory now, + update PKGBUILD.

https://wiki.archlinux.org/index.php/AURINFO