Tchannel

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

- Introduced new server API through methods
``tchannel.TChannel.thrift.register``, ``tchannel.TChannel.json.register``,
and ``tchannel.TChannel.raw.register`` - when these methods are used,
endpoints are passed a ``tchannel.Request`` object, and are expected to
return a ``tchannel.Response`` object or just a response body. The deprecated
``tchannel.tornado.TChannel.register`` continues to function how it did
before. Note the breaking change to the top-level TChannel on the next line.
- Fixed a crash that would occur when forking with an unitialized ``TChannel``
instance.
- Add ``hooks`` property in the ``tchannel.TChannel`` class.
- **BREAKING** - ``tchannel.TChannel.register`` no longer has the same
functionality as ``tchannel.tornado.TChannel.register``, instead it exposes
the new server API. See the upgrade guide for details.
- **BREAKING** - remove ``retry_delay`` option in the ``tchannel.tornado.send``
method.
- **BREAKING** - error types have been reworked significantly. In particular,
the all-encompassing ``ProtocolError`` has been replaced with more
granualar/actionable exceptions. See the upgrade guide for more info.
- **BREAKING** - Remove third ``proxy`` argument from the server handler
interface.
- **BREAKING** - ``ZipkinTraceHook`` is not longer registered by default.
- **BREAKING** - ``tchannel.sync.client.TChannelSyncClient`` replaced with
``tchannel.sync.TChannel``.

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

- Raise informative and obvious ``ValueError`` when anything
but a map[string]string is passed as headers to the ``TChannel.thrift`` method.
- First param, request, in ``tchannel.thrift`` method is required.

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

- Raise ``tchannel.errors.ValueExpectedError`` when calling a non-void Thrift procedure
that returns no value.

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

- Introduced new top level ``tchannel.TChannel`` object, with new request methods
``call``, ``raw``, ``json``, and ``thrift``. This will eventually replace the
akward ``request`` / ``send`` calling pattern.
- Introduced ``tchannel.thrift_request_builder`` function for creating a
request builder to be used with the ``tchannel.TChannel.thrift`` function.
- Introduced new simplified examples under the ``examples/simple`` directory, moved
the Guide's examples to ``examples/guide``, and deleted the remaining examples.
- Added ThriftTest.thrift and generated Thrift code to ``tchannel.testing.data`` for
use with examples and playing around with TChannel.
- Fix JSON arg2 (headers) being returned a string instead of a dict.

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

- Implement VCR functionality for outgoing requests. Check the documentation
for ``tchannel.testing.vcr`` for details.
- Add support for specifying fallback handlers via ``TChannel.register`` by
specifying ``TChannel.fallback`` as the endpoint.
- Fix bug in ``Response`` where ``code`` expected an object instead of an
integer.
- Fix bug in ``Peer.close`` where a future was expected instead of ``None``.

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

- Add support for specifying transport headers for Thrift clients.
- Always pass ``shardKey`` for TCollector tracing calls. This fixes Zipkin tracing for Thrift clients.