add support for IPv6 lookups, including documentation and updated DB files

Here's the code, and thanks for your help fixing my Clojure bumbling. :-)

Thanks also to rightføld on StackOverflow (http://stackoverflow.com/users/1804599/rightf%C3%B8ld) for help with macros:
http://stackoverflow.com/questions/26738065/how-can-i-add-a-second-parameter-to-a-macro-in-clojure/26738500#26738500