Bibliography: add and update references
Appendix: clean up source code and rewrite captions
Preamble: remove headers and clean up unused commands
References: Add reference for TikZ and PGF

Conflicts:
	paper.tex
Introduction: Add MDS acronym to first use of martingale difference sequence
Bibliography: fix recurring bibtex error in merlevede and peligrad
Misc: add package to put commas between multiple footnotes
Merge branch 'cleanup'
Massive intertwined rewrite

This commit squashes together a ton of edits to the main paper.
It's horrible. sorry.
Empirics: clean up table listing Goyal and Welch variables

This commit adds the booktabs and tabularx packages to the
preamble and moves the list of Goyal Welch variables to
a booktabs table.

The first table was smushed into the bibliography; that's been fixed
now and it's on its own page.
Rewrite empirical analysis

This commit rewrites the empirical section of the paper, to try
to better motivate it and make it easier to understand. Hopefully
it's better.
Merge revisions to empirical analysis

The branch we're merging is an extensive rewrite of the
empirical analysis. It may need to be tweaked before
submission, but should be pretty much done.