fixes mulitple entry record comparison by order canonicalization

On rr's that have more than one entry, for example MX records, the
order they are in the zone file may not match the order they are in
the the AWS pull of the record.  This leads to needless deletes and
adds when doing an import --replace.
Hash table added for comparing current to new zone information.

The original algorithm went O(n^2) during the comparison.  This resulted
in hilariously long runtimes for moderate sized zones.  This crudely smashes
a hash table (dict to be exact) into the process, dramatically reducing the
comparison time.
Merge branch 'c14n-rr'