Fixed PHP-537: Update limits according to default (16MB) or server info (maxMessageSizeBytes).
Throw an exception when a batch insert goes over the limit.

This will be addressed later, with the implementation of PHP-705.
Updated patch with comments from Hannes' review.
Fixed test case after message format changes.
Merge PR#323 (PHP-537)

* pr/323:
  Fixed test case after message format changes.
  Updated patch with comments from Hannes' review.
  Throw an exception when a batch insert goes over the limit.
  Fixed PHP-537: Update limits according to default (16MB) or server info (maxMessageSizeBytes).