we should probably use ruby's built-in ipaddress capabilities:

<pre>
  require 'ipaddr'
  ip = Addrinfo.ip(ip_address)
  ip.ipv4? and not ip.ipv4_loopback?
rescue
  false
</pre>

One problem is that `Addrinfo` is new in ruby 1.9.3, so to make this change in a patch release we'd probably need to use the older `IPAddress` methods, and keep our regex's above to detect the loopback and APIPA addresses.