Updated bulk_add records for better reliability

Firstly, if you submitted more than 100 records an exception would be
thrown because that is the maximum records in a single request. After
fixing that error and testing a domain with around 850 records I would
get very inconsistent results, timeouts, and NoneType exceptions from
PyRax. I've been able to get consitent results by breaking up the
batches into groups of 20.
worked around error with PyRAX/CloudDNS && Added Debug Option