Implement regex filtering. Will use this to find manual pages.

Squashed commit of the following:

commit 1f58e3363033964f0dabbc0085d34af259c65bdc
Author: Edd Barrett <vext01@gmail.com>
Date:   Sat Nov 2 13:53:10 2013 +0000

    Implement regex filtering and test.

commit f5fc3f3bcb7078ea9eb4b2a9b705305f647f69d2
Author: Edd Barrett <vext01@gmail.com>
Date:   Sat Nov 2 13:02:18 2013 +0000

    Improved filespec parsing