Vcrpy Versions Save

Allow injection of persistence methods + bugfixes (thanks @j-funk and @IvanMalison) Support python 3.6 + CI tests (thanks @derekbekoe and @graingert) Support pytest-asyncio coroutines (thanks @graingert)

• Added a fix to httplib2 (thanks @carlosds730)
• Fix an issue with aiohttp (thanks @madninja)
• Add missing requirement yarl (thanks @lamenezes),
• Remove duplicate mock triple (thanks @FooBarQuaxx)

vcr.py now supports aiohttp!

• Add support for boto3 (thanks @desdm, @foorbarna).
• Fix deepcopy issue for response headers when decode_compressed_response is enabled (thanks @nickdirienzo)

[#188] additional_matchers kwarg on use_casstte. [#191] Actually support passing multiple before_record_request functions (thanks @agriffis).