Uamqp

- Added Certifi as a depedency to make OpenSSL certs dynamic.
- Added [verify]{.title-ref} option to authentication classes to allow
setting custom certificate path (for Linux and OSX).

- Fixed memory leak in async receive.
- Removed close_on_done argument from client receive functions.
- Added receive iterator to synchronous client.
- Made async iter receive compatible with Python 3.5.

- Fixed SSL errors in manylinux wheels.
- Fixed message annoations attribute.
- Fixed bugs in batched messages and sending batched messages.
- Fixed conflicting receiver link ID.
- Fixed hanging receiver by removing queue max size in sync clients.
- Added support for sending messages with None and empty bodies.

- Added message send retry.
- Added timeouts and better error handling for management requests.
- Improved connection and auth error handling and error messages.
- Fixed message annotations type.
- SendClient.send_all_messages() now returns a list of message send
statuses.
- Fixed OpenSSL platform being initialized multiple times.
- Fixed auto-refresh of SAS tokens.
- Altered [receive_batch]{.title-ref} behaviour to return messages as
soon as they\'re available.
- Parameter [batch_size]{.title-ref} in [receive_batch]{.title-ref}
renamed to [max_batch_size]{.title-ref}.
- Fixed message [application_properties]{.title-ref} decode error.
- Removed MacOS dependency on OpenSSL and libuuid.

- Added management request support.
- Fixed message-less C operation ValueError.
- Store message metadata in Python rather than C.
- Refactored Send and Receive clients to create a generic parent
AMQPClient.
- Fixed None receive timestamp bug.
- Removed async iterator queue due to instabilities - all callbacks
are now synchronous.

- Added support for asynchronous message receive by iterator or batch.
- Removed synchronous receive iterator, and replaced with synchronous
batch receive.
- Added sync and async context managers for Send and Receive Clients.
- Fixed token instability and added put token retry policy.
- Exposed Link ATTACH properties.
- A connection now has a single \$cbs session that can be reused
between clients.
- Added C debug trace logging to the Python logger (\'uamqp.c_uamqp\')