Add cygport completions provided by Andrew Schulman

Squashed commit of the following:

commit a396c5e95a9987ea8ce6e057910131886d1b9695
Merge: bfd1951 f329530
Author: Konrad Borowski <x.fix@o2.pl>
Date:   Mon Dec 1 17:54:02 2014 +0100

    Merge branch 'master' of https://github.com/andrex-e-schulman/fish-shell into andrex-e-schulman-master

commit f32953064e1083be48c785f6763a4f6da6caf54b
Author: Andrew Schulman <andrex-e-schulman@users.noreply.github.com>
Date:   Mon Dec 1 05:34:29 2014 -0500

    improve descriptions of pkg and diff

commit 81def0fb3086de639453eacb2eab174f3c67b976
Author: Andrew Schulman <andrex-e-schulman@users.noreply.github.com>
Date:   Mon Dec 1 04:51:20 2014 -0500

    simplify cygport option descriptions

commit 4d84eb3e5cadbf4b1f6210552256e5373360d8fb
Author: Andrew Schulman <andrex@5200-glenwood.net>
Date:   Mon Dec 1 04:32:47 2014 -0500

    add command descriptions to share/completions/cygport

commit c7ff7e4fa21dad19aeda0ae837e22bf4cff20a79
Author: Andrew Schulman <andrex@5200-glenwood.net>
Date:   Mon Dec 1 03:09:00 2014 -0500

    add share/completions/cygport.fish