Minor Makefile tweaks.
Rewrite Docx.hs and Reducible to use Builder.

The big news here is a rewrite of Docx to use the builder
functions. As opposed to previous attempts, we now see a significant
speedup -- times are cut in half (or more) in a few informal tests.

Reducible has also been rewritten. It can doubtless be simplified and
clarified further. We can consider this, at the moment, a reference for
correct behavior.
Merge pull request #1539 from jkr/builderRewrite

Rewrite Docx.hs and Reducible to use Builder.
Docx reader: Fix bug in character styles.

Style handling has been cleaned up, but introduced a bug here. There
wasn't previously a test to catch it.
Docx reader: Test for character styles.
Docx reader: Remove unnecessary plural functions

functions like runElemsToInlines and parPartsToInlines are just defined
in terms of concatting and mapping their singular
version (e.g. `runElemToInlines`). Having two functions with almost
identical names makes it easier to introduce errors. It's easy enough to
just concat and map inline, and it makes it clearer what is going on in
the code.
Merge pull request #1540 from jkr/charStyles

Char styles
Release checklist: No longer need to compile pandoc-dingus.

trypandoc is used.
Updated README in templates to indicate templates license.

The templates are duel licensed, BSD3 and GPL2+.
Makefile:  Added 'quick' target.
Markdown writer: don't escape $, ^, ~ when extensions are deactivated.

`tex_math_dollars`, `superscript`, and `subscript` extensions,
respectively.

Closes #1127.
Include row width in table rows.

Added a property to all table rows where the sum of column widths
is specified in pct (fraction of 5000).
Simplify row width calculation.