Sqs-workers

Changed

- API: Processor.process() now returns the result of the execution (9)
- Documentation: Improved README. Added the "Contributing" section and improved the
testing documentation.

Fixed

- Fixed batch logic (11)

- Updated README with examples on how to process a dead-letter queue in-place
- Added a way to add tasks in batch

Changed

- Declared support for Python3.8
- Made sqs-workers work better in Python2 / Python3 mixed environment

Changed

- Deprecated calling AsyncTask(**kwargs). Now, if you want to run it
synchronously, you should use AsyncTask.run(**kwargs) instead.
Use AsyncTask.delay(**kwargs) as always to add the task to the queue.

Changed

- Removed support for batched processors
- On top of existing sqs.processor("queue", "job_name") added
sqs.raw_processor("queue") to process unstructured messages from the qeueue
- Extracted functions to create and delete queues for SQSEnv to a separate module
- Remove most of the "proxy methods" for SQSEnv: purge_queue, drain_queue,
process_queue, process_batch, get_raw_messages. SQSEnv.queue() has to be used
instead.

Added

- Added support for baked async tasks (async tasks + arguments)

Fixed

- Fixed DeadLetterProcessor with FIFO queues

Changed

is_deadletter() and get_deadletter_upstream_name() extracted from
methods to independent functions.