Snapstream

- now calling producers poll method by default

- bumped dependencies

* Added topic slicing/indexing.

* Added ability for user to define produce logic by passing `pusher` function to `Topic`.

* Added [CLI docs](https://snapstream.readthedocs.io/en/latest/cli.html).

* Added kafka integration tests.

* Fixed bug where some log entries were not passing through the log filter.

* Fixed CLI bug where escaping '$' in config failed.

* Fixed bug where CLI would create folder if cache path didn't exist.

* Fixed bug where CLI topic value was decoded even if it was already decoded using a codec.

* Disabled setting loglevel.

* Added [readthedocs](https://snapstream.readthedocs.io) documentation.

* Fixed keyboardinterrupt to stop the program.

* Added support for argumentless handler functions.

* Moved kafka configuration warning log filter.

* Added function to get admin client.

* Added 'auto.offset.reset': 'earliest' in examples.

* Using Cache contextmanager now returns a Cache instance.

* Added escape option for for literal values starting with $ in CLI config file.

* Using absolute cache path in CLI config file.

- providing cli command to read data from Topic/Cache
- replacing Cache default "with_ttl" access_type with "read_write"
- allow "yield" to be used in handler functions

- allow user to define producer callback and consumer poller

- factoring out functions included in other functions
- enabling users to pass custom producer/consumer handlers
- moving dry argument to Topic level
- triggering manual commits when enable.auto.commit is false
- no longer flushing after each message, `flush.messages` or `flush.ms` can be used instead
- - fixing types