The big one is probably that tagrenderers can output blocks
such as tables. We also slurp sections, so that subsections
become a part of the above sections children.
The FSI evaluator adds about 1000% of runtime for testing, so
I added a NullEvaluator.
I also added default constructors for many of the base elements.
The parsers are not yet done, but you can do very rudimentary tables.
The AST has gotten a large update, and it is pretty much complete.
