support custom AWS.Config() instead of requiring parameters be manually mapped

[knksmith57]

The Dyno factory only supports a small subset of the available AWS configuration options because it plucks certain properties from the options hash and passes them into the AWS.DynamoDB constructor.

This is problematic for consumers wishing to have fine-grain control over the behavior of the AWS SDK.

Dyno should support using a custom AWS.Config instance to configure the AWS SDK.