use regex to detect state/local domains ending in .us

Based on http://en.wikipedia.org/wiki/.us#Second-level_domains_for_states, there are some basic rules around state/locality `.us` domains.
Either:

`(ci|town|vil|co).<locality>.<state>.us` 

or 

`*.(state|dst|cog).<state>.us`

So:

1. Remove domains matching this regex from the list
2. Add in a check pre-public suffix to see if domains match this regex

Added bonus: It makes `domains.txt` smaller.