Event streaming hangs waiting for newline in Docker Desktop for Mac 2.2.0

As currently written, aiodocker expects docker events to be separated by newlines -- jsonstream.py calls `response.content.readline()`. For reference, docker-py reads chunked data and uses `JSONDecoder.raw_decode()` in case there are extra characters.

The downsides of this assumption (newline delimiters) are documented [in this moby issue (20119)](https://github.com/moby/moby/issues/20119).

In any case, Docker Desktop for Mac 2.2.0.0 causes aiodocker to hang waiting for a newline which never occurs even while multiple events are received.

Docker Desktop for Mac 2.1.0.5 works without issue and apparently separates events by newlines.

Python 3.7.5
MacOS 10.15.3
Docker Desktop for Mac 2.2.0
aiodocker 3.6.2