Make the list a bit easier to handle in scripts (colon does not have
special regex meaning).

Also im human-readable contexts, dot makes it more likely to confuse the
string with with filename (eg. `foo.bar`.)  But then again, it's better
for humans to go a bit further and decorate the reference, eg.
`foo:bar()` or `foo:$BAZ`.  (Doing that in default output would make
them hard to parse, though.)

'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.