* Markdown writer now includes a blank line at the end
of the row in a single-row multiline table, to prevent it from being
interpreted as a simple table. Closes#4578.
* Markdown reader does a better job computing the relative width of
the last column in a multiline table, so we can round-trip tables
without constantly shrinking the last column.
* New module: Text.Pandoc.Writers.Ms.
* New template: default.ms.
* The writer uses texmath's new eqn writer to convert math
to eqn format, so a ms file produced with this writer
should be processed with `groff -ms -e` if it contains
math.
