adding callbacks support to BatchQuery
removing `batch` from the list of args passed to BatchQuery callbacks
switching to list as BatchQuery callbacks collection + add_callback() API
fix for "ValueError: 'column_name' is not in list" error on sync_table for models with primary keys only

https://github.com/cqlengine/cqlengine/issues/175
more blah for primary-key-only table sync_table test
cleaning up batch callback docs
Merge branch 'pull-178'
fixed issue with timestamp and DST
timestamp as a long wasn't being assigned
Removed cql monkey patch in favour of Quoter to allow Bytes support
Added a test to show the problem with Text values and '0x' prefix
updating changelog and version