NF: automatic slides conversion with pandoc

Use pandoc parsing of tex files to parse tex file, build notebook.
RF: extend the converter somewhat

Make the code replacement in the tex file a little less fragile with a
very crude parser.  Extend the things the converter can handle.
RF: edit tex for errors and math in \text

Make pandoc happy by editing tex for some tex errors, and for math
embedded in math, such as:

$H = \text{$H$}$

Just remove the dollars from the embedded math because it messes up
pandoc parsing, so we need to go back and fix the converted document
latex afterwards.
NF: add newline after span to make md lists work

Need a newline after the span to give an extra line after text, in order
for lists to render correctly.
FIXME
NF: added data needed for final_review notebook
NF: remainder of notebooks converted

Notebooks here with some hand editing for editing to the underlying tex,
and some formatting.
Merge pull request #2 from matthew-brett/auto-convert-at-last

NF: automatic slides conversion with pandoc