Add Async IO support

[dszakallas]

I added a proof of concept implementation for this lib whihc uses async http: https://aiohttp.readthedocs.io/en/stable/index.html I don't know yet how to include this code in a way that does not break interpreters below 3.5. I want to avoid putting it into a string and execing.

I am not very familiar with Python yet, so I appricieate any help on this. Thanks!