Yarpc

------------------

- Nothing changed yet.

------------------

- All transport-level errors get serialized to/from ``yarpc.errors.BadRequestError``
or ``yarpc.errors.UnexpectedError``.
- Default ``yarpc.transport.http.HTTPInbound`` port to 0, which will result in the
os choosing a random available port when ``start()`` is called. This port will be
available on ``HTTPInbound.port``.

------------------

- Fix JSON decode failing on empty headers.

------------------

- Fix pin to tchannel, use ``tchannel>=0.24,<0.25``.

------------------

- **BREAKING** Revamped the client API.

------------------

- Fix pin to tornado, use ``tornado>=4.3,<5``.