Findssh

Using single-threaded asyncio vs. ThreadPool is twice as fast or more, using just a single thread and coroutines, all standard library for Python >= 3.5. The asyncio benefit is particularly noticeable on limited resource systems like Raspberry Pi.

Also, now Matlab works really fast as well calling the Python coroutine code

Added Matlab `findssh.m` to reuse the Python API.

Improved test coverage, corrected empty return from multi-threaded exec

just a version bump

Streamline CI template

use `setup.cfg` instead of `setup.py`

SImplify/uniformize command line to just `findssh`, thereby also templatizing self-test

README: rst=>md