moar binary

This switches kA, wrapKb, tokenids, and tokendata to binary in mysql and also to Buffers in the app layer.

The majority of the diff is switching around buffer <-> string conversions. The other notable changes are:

* use `deepEqual` in the tests that compare Buffers
* changed log.js to convert logged buffers to hex strings. Otherwise they get output as an array of digits :poop: 
* ensure HAWK ids are hex before querying the DB
* renamed `token.id` to `token.tokenid` because HAWK expects `token.id` to be a string. Made `token.id` a getter.
* added `bufferIsNull` function to replace hex string comparison


@chilts I hope this doesn't affect your work too much.

@rfk @chilts r?

Closes #305