TODO.md

• Replace stuff like res.get('header').get('user') to direct access res.header.user
• Check if transaction/retry errors are being checked correctly, i'm not sure if this protobuf librarie can do type checking.
• Map this errors https://github.com/cockroachdb/cockroach/blob/master/proto/errors.proto#L131, check this https://developers.google.com/protocol-buffers/docs/techniques#union to determine implememtantion, you should also redo the batch union interface
• Check if https://github.com/herenow/roachjs/blob/master/lib/txn_sender.js#L36 is working as expected.