Move citation and version information into main LaTeX file

This commit removes the separate VERSION.tex and CITATION.bib files
and moves their contents to core_econometrics.tex. It just cleans
things up a little.
Increase left margin in code environments
Decrease margins and increase font size

This commit reduces the margin size and increases the font; the net
effect is to print to fewer papers and to look less "designy." A few
lines and equations are rewritten so that the line breaks aren't
horrendous, but there are still problems.