table: trim cells, fix escaping, cleanup (#4)

* Include table alignment when rendering LaTeX
* Include table alignment when rendering man (preserving default centre
  alignment here)
* Trim table cell interiors
* Expand test cases
* Fix escaping behaviour
* Do not use enum for alignment
* Do not collide against stdlib `ispunct`
* Cleanup pipe code
* Don't reparse matched rows

Author: Yuki Izumi