Provides commands for explicitly unfilling (ie. unwrapping)
paragraphs and regions, and also a command that will toggle between
filling and unfilling the current paragraph or region.

Based initially on Xah Lee's examples, and later rewritten based on an article by Artur Malabarba.
  http://endlessparentheses.com/fill-and-unfill-paragraphs-with-a-single-key.html
  http://xahlee.org/emacs/emacs_unfill-paragraph.html
  http://xahlee.org/emacs/modernization_fill-paragraph.html