Fix #129: use transaction ID from connection's own transaction.
Fix #131:  return datetime w/ UTC zone.
Fix #132:  enforce 64-bit ranges on long values for protobuf attrs.
Incorporate feedback from @dhermes.
Don't pass transaction ID to connection.rollback_transaction().

Feedback from @dhermes.
Merge pull request #182 from tseaver/132-enforce_int64_bounds_for_protobuf_values

Fix #132:  enforce 64-bit ranges on long values for protobuf attrs.
Removing keyword "type" from storage.acl.
Using more descriptive entity_type instead of type_.
Merge pull request #180 from tseaver/129-rollback_using_connection_xact

Fix #129: use transaction ID from connection's own transaction.
Merge pull request #156 from dhermes/fix-overloaded-keyword

Removing overloaded global "type" from storage.acl.
Merge pull request #181 from tseaver/131-return_dateimtes_w_utc_zone

Fix #131:  return datetime w/ UTC zone.