'sfdoc' is easier to type and resembles 'pydoc' and 'perldoc' so it's
even easier to remember.

Great rewrite with revamped CLI, many added features and bugfixes.

 *  New CLI optimized for simple use.  Default action is to show
    module doc in manpage viewer.

 *  Respects variable documentation.

 *  Respects module documentation (first stray docstring).

 *  Can export (ugly but usable) module docs as Markdown, POD or
    manpage.

 *  Dropped useless features as --cat (one can always open the file)
    or display of partial documentation.

 *  Provided more rich usage hint.

 *  Rewrote tests with focus on more probable scenarios.

Mostly ugly (at least how lintian sees it) but first working version.