RemexHtml tidy driver with p-wrapping

RemexHtml tidy driver with p-wrapping

Pull in the RemexHtml library, which is an HTML 5 library I recently
created.

RemexCompatMunger mutates the event stream, inserting <mw:p-wrap>
elements where necessary, and occasionally taking even more invasive
action such as reparenting and removing nodes maintained in Serializer's
tree.

RemexCompatFormatter produces a MediaWiki-style serialization which is
relatively compatible with existing parser tests. It also does final
empty element handling, including translating <mw:p-wrap> to <p>

Tests are imported from both Html5Depurate and Subbu's pwrap.js.

Depends-On: I864f31d9afdffdde49bfd39f07a0fb7f4df5c5d9
Change-Id: I900155b7dd199b0ae2a3b9cdb6db5136fc4f35a8