Update for utemplate refactors.
Add start_html() convenience function.
Add sendfile() action to send static file.
Add support for POST values decoding.
Add render_str() to render template as a string.

TODO: implement more efficiently.
Add jsonify() call.
Store URL match object as req.url_match (to extract URL params, etc.).
Release 0.3.
Convert to package, add unbloated implementation of parse_qs().
Release 0.4.