Allow creating and deleting entries with more than one value

change the change function to take either a single string for value or
a sequence of values and generates the appropriate record sets.

The extra 1 in (zf-xml/xml1-> rr :ResourceRecords :ResourceRecord :Value zf-xml/text)
prevented deleting multi-value records because the values where trunkated causing
amazon to reject the request.
add TXT and MX records, and more examples in README.md
add AAAA records for ipv6 and don\'t drop otional arguments
make update-record return a maningful value on both success and failure
Fix find for accounts with more than 100 entries

Amazon paginates results into groups of not more than 100, and find
was using a single call to get all the entries, and then filtering
the desired entries from that. This was missing entries on accounts with
more than 100 items.
Merge pull request #3 from thearthur/master

Add MX and TXT records and Allow editing of multi-value records such as A records