Things to do in multiple notebooks

[rjleveque]

A list of some things that we need to do still:

1. Put github links for all exact_solvers codes in each notebook?
2. If we put these in, modify fix_latex_file.py so it doesn't generate two footnotes with github links.
3. Decide whether to use [Shallow_water.ipynb](Shallow_water.ipynb) to refer to other chapters, or [Shallow_water](Shallow_water.ipynb) and make consistent.
4. We use subscripts q_l some places and q_\ell others. Make consistent.
5. Add more references to other books or papers?
6. Improve the looks of riemann.html generated by make_html_bib.sh. Currently the entries are put in the order they appear in riemann.bib, not in alphabetical order. Also some have first names, others not.
7. Move utility scripts in utils and change links as needed.
8. Make a set of files documenting how we do things and the tools we use, maybe as .md files in a doc folder? Fix the link to these in Preface.ipynb.
9. Fix up the Dockerfile if necessary and make sure everything works on binder.