Remove lxml requirement for parsing LinkedIn data.

Falls back on xml.etree.ElementTree.
Typos is comments + contributors
Remove lxml requirement for parsing LinkedIn data.

Falls back on xml.etree.ElementTree.

Pulled from https://github.com/michaelolson/simpleauth/commit/84381aa299df6ce4fbb354f3d80b0a5d92c8e28b
Closes #18.
Thanks @michaelolson!