Sqlalchemy-drill

Fixed

- Fix a leaked StopIteration from a generator.

Fixed

- Add 'properties' as a reserved word.

Changed

- Fixed type casting bug which caused queries that returned null date or time
values to raise an error in _drilldbapi.py.

Changed

- Add an impersonation_target parm to drill+sadrill URLs. When present,
this parameter will be converted to a userName property in POSTs made to
/query.json.

Fixed

- Backwards compatibility with Drill < 1.19, limited to returning all data
values as strings. Users not able to upgrade to >= 1.19 must implement their
own typecasting or use sqlalchemy-drill 0.3.

**N.B.**: The drill+sadrill dialect in this release is not compatible with Drill
< 1.19.

Changed

- Rewrite the drill+sadrill dialect using the ijson streaming parser.