+ Removed `--man1`, `--man5` options (breaking change).
+ Removed `Text.Pandoc.ManPages` module (breaking API change).
+ Version bump to 1.15 because of the breaking changes, even
though they involve features that have only been in pandoc
for a day.
+ Makefile target for `man/man1/pandoc.1`. This uses pandoc to
create the man page from README using a custom template and filters.
+ Added `man/` directory with template and filters needed to build
+ We no longer have two man pages: pandoc.1 and pandoc_markdown.5.
Now there is just pandoc.1, which has all the content from README.
This change was needed because of the extensive cross-references
between parts of the README.
+ Removed old `data/pandoc.1.template` and