fastannotate: record some TODO items from indygreg's review
Some of these I'll address more or less right away, but some will take
a while for us to resolve.
Differential Revision: https://phab.mercurial-scm.org/D4200
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.