Modify to handle larger queries.

Your package was just what I was looking for to allow Salesforce to be used as a Django backend, but unfortunately it doesn't work for the larger queries I'll be needing. The Salesforce API only returns 500 records per call, so it is necessary to make multiple calls when a select query will return more than that many records. Also, because of this, I didn't think it was necessary to fetch results in chunks of 100.(GET_ITERATOR_CHUNK_SIZE), so I didn't include that code in my changes.