getBatchResult does not support CSV content type

It would appear that when creating a job with the CSV content type and uploading CSV batches most requests (those made by getJobStatus, getBatchInfo, etc) transmit response data in XML format which is parsed successfully. However ,`/services/async/40.0/job/xxx/batch/xxx/result` returns its response in CSV format (the format specified for the job). The getBatchResult method attempts to parse this data as XML and raises an exception: `XmlPullParserException only whitespace content allowed before start tag and not " (position: START_DOCUMENT seen "... @1:1)`. It looks like fixing this will require some new work to deserialize a CSV as a `Result` object.