* check-in of http://codereview.appspot.com/25082
* check-in of http://codereview.appspot.com/25082

  Currently, a comment in the IP method explains the complicated nature of this
  method as "caused by the confusing nature of v4 in mapped in v6 addresses". This
  is probably based on the misconception that 1.2.3.4 is a valid v4 as well as a
  valid v6 address. According to RFC 4291 2.2.3 (and IPv6._is_valid_ip), this is
  not the case; after weeding out a bug in IPv4._is_valid_ip (see Rietveld issue
  #25081 [1]); trying IPv4 before IPv6 does not cause any testcases to fail.
  


simplegeo/ipaddr,simplegeo/ipaddr