* Mark runtests helper executable
* Bump required version of asgiref
We're probably making our life easier when we keep the Channels
dependencies roughly in sync. As a 1.0 release was made, I suggest to
require it.
* Simplify tox and Travis configuration
I hopefully simplified the tox configuration by following what I did in
the other four Channels projects.
I then had a good look at tox-travis and decided to remove it. It does
add a layer of indirection with, IMHO, not enough gain. To understand
what Travis is doing, one would need to consider two files (and
understand tox-travis) instead of just one file. It also introduces
another point of failure. What pushed me over was that there's a bug
with env matching (https://github.com/ryanhiebert/tox-travis/issues/55)
and tox or tox-travis seem to mask an Exception
(https://travis-ci.org/django/channels/jobs/195950971#L195) that would
be hard to debug.
The draw back is that we duplicate the Django dependency matrix, and the
commands that are executed in Travis and tox. We could add a "--with-qa"
flag to runtests.py to have it execute flake8 and isort to rectify the
latter.
I extracted test dependencies as I did for asgi_redis.
* Document supported versions
