Add code to handle selects that return more than 100 records

The Salesforce API only returns 500 records per call, so it is
necessary to make multiple calls when a select query returns more than
500 records. Because of this, it's not necessary to fetch results in
chunks of 100.(GET_ITERATOR_CHUNK_SIZE)
Merge branch 'master' of git://github.com/reggied/django-salesforce into reggied-master
added comment for details on nextRecordsUrl, updated AUTHORS file