Add logging sink

[benkehoe]

The CloudFormation resource provider python framework doesn't support stdout logging, it only picks up logs emitted using logging [1]. A sink that submits logs that way would allow this library to be used easily with that framework.

[1] https://github.com/aws-cloudformation/cloudformation-cli-python-plugin/blob/master/src/cloudformation_cli_python_lib/log_delivery.py