Load from HTML

[gkellogg]

• Use lxml.html to load HTML and parse in load_html.
  • For HTML, the API base option can be updated from base element.

Note this is a PRI into 1.1-expansion.

[gkellogg]

Note the 3.4 failure:

Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-phouehag/lxml/

Do we want to bump the minimum version to 3.5 or figure out how to do this conditionally?

[dlongley]

@davidlehn, please review.