Add multidomain support via subdomains

This updates Border Patrol from v0.1 to v0.2

Hostname based service authentication is done via the first subdomain
present, e.g. business.example.com maps to "business". This takes
precedence over url-resource based routing. So, let's say you have your
enterprise mount point at '/ent', the url of business.example.com/ent
would route to the 'business' service, not the 'enterprise' one.

This hostname based service is meant to handle a lot of edge cases
surrounding url-resource based routing, especially those surrounding
legacy applications that don't easily respect being mounted to a
particular resource-route.

Additional work has been done to simplify and modularize the various
components of Nginx configs. Shared locations are now in separate files
that can be included into server config blocks.
Merge pull request #42 from trane/multidomain

Add multidomain support via subdomains