Fix XML pretty-printing & import __version__ into setup.py

A pleasure to lend a hand. Thank you for accepting my previous pull request. ☺︎

Quoted from my commit:
>Fixes #11.
>
>Technically speaking, all whitespace is significant in XML as described here:
>http://www.oracle.com/technetwork/articles/wang-whitespace-092897.html
>
>For practical purposes, as long as we leave TEXT literals alone (text between
>elements), we should be OK.
>
>xmlformatter does not depend on any external Python libraries and appers to do a great job,
>xml.dom.minidom is known to be terrible as noted here:
>http://ronrothman.com/public/leftbraned/xml-dom-minidom-toprettyxml-and-silly-whitespace/