Extensive rewrite of the paper's theoretical component

This commit is a major rewrite of the paper's theoretical component,
including both the in-sample and out-of-sample results. The in-sample
proofs still need to be completed, but otherwise this part of the
paper is more or less ready to go.
Revise Monte Carlo presentation

This commit edits the presentation of the Monte Carlo results,
hopefully making them seem more important and making them
easier to follow.

It also fixes several bugs in the graphs and converts the
presentation of the F-test results to a table.
Revise empirical write-up

This commit makes several minor changes to the empirical section.
Tweak intro to appendix
Correct stupid spelling mistake in title of appendix
Rough version of proof for in-sample statistics