Asyncgenerators: Tests + Error handling

Python 3.7 needs that

Monkey-patch asyncio's get_event_loop{,_policy} calls to return the
currently-running loop / Tri...

reported to be unstable
one of these is disabled in asyncio

Closes #15.

https://github.com/python-trio/trio-asyncio/issues/11

Fix link to the docs in README.

intermittent travis failure

for now

Sorry about that.

otherwise subtasks won't see the main event loop

Fix project URL in setup.py

was always False (when running async). Oops.

also didn't work because auto-async-ification
does not work in unittest classes

There is no good trade-off here …

TODO: think of a sensible name for calling this from asyncio.

Problem: $THING calls loop.stop() but then doesn't immediately return.

* split the processing p...

and accept "standard" arguments

TODO: resolve some of the more interesting failures.

we don't want to test asyncio itself
the tests run into depreciation warnings on Python 3.7

… and yes, they are broken.

not testable due to async fixture