see http://microformats.org/wiki/microformats2-parsing-issues#ignore_u-camelCase_properties for background
allow only a basic set of tags, and remove any non-mf2 classes closes #2
if a property such as `in-reply-to` is an h-cite, the URL is still returned as the `in-reply-to` value, and the h-cite object is available in a different part of the response. closes #6