Start of Diffs

Requesting we pull in this checkpoint commit on parsing out diffs based on rules.

* Split notice module into components
* Move core grammar bits out of internal_citations
* Separate out the xml parsing per section into a separate function
* Using that parser, make a first pass at the rules and spit out mentioned sections

Obviously there's a lot more to do, but I wanted to get this in so that our source trees don't diverge too too much.