Add DynamoDB storage driver

[jkmathes]

A storage plugin to allow storing slack-machine data into AWS DynamoDB

Optional slack-machine settings introduced:

DYNAMODB_ENDPOINT_URL - specifies an optional alternate endpoint, for local bot testing DYNAMODB_KEY_PREFIX - an optional prefix to use within the key lookup. Defaults to SM: DYNAMODB_TABLE_NAME - specifies the table to use in DynamoDB. Defaults to slack-machine-state DYNAMODB_CREATE_TABLE - optionally -create- the table to be used in DynamoDB. Defaults to False DYNAMODB_CLIENT - if custom configuration is needed for the DynamoDB client, an optional client can be specified here

[DonDebonair]

Looks beautiful! And the timing is great as well. Just moved to a new job that uses AWS as cloud provider. So thanks for this!

[DonDebonair]

I do have one request: could you document this new storage backend here?

[jkmathes]

It should be updated (and now, with the correct formatting!) - thoughts?

[DonDebonair]

This was fixed in v0.27.1. It has only been implemented for the upcoming async version of Slack Machine