asyncio.async() deprecation

[linuxdaemon]

The asyncio.async() function has been deprecated since Python 3.4.4, replaced by asyncio.ensure_future() and in Python 3.7, naming functions or variables async or await will throw an error due to them being converted into full keywords.

We could possibly still maintain compatibility back to 3.4.2 by writing a wrapper function in the core around AbstractEventLoop.create_task()

@edwardslabs I could go either way, it's up to you

[linuxdaemon]

175 fixes this without sacrificing version compatibility at all, I didn't think about writing a version dependent wrapper function before.