Add Async classes to typehinting.

[rowillia]

No description provided.

[vlasovskikh]

The corresponding PR with the stubs is python/typeshed#30.

[o11c]

What's the upgrade plan, since Python 3.5 has been released without this, and the standard library takes precedence over third-party installs?

[gvanrossum]

PEP 484 and typing.py are provisional, so we can add it to 3.5.2 (it's too late for 3.5.1 though, rc1 already went out).

[gvanrossum]

So I merged this into Python 3.5 and 3.6, but after I was done I realized that the tests are now broken for Python 3.2-3.4 (because the added tests use the async/await keywords). Would you be willing to make a new PR that moves those tests (and only those) to a separate file? We're using the same pattern for asyncio, where there's a separate file test_pep492.py containing tests that are syntactically invalid in earlier Python versions. (Because it's syntax, you can't use @Skip decorators.)

[rowillia]

@gvanrossum sure thing.

[vlasovskikh]

We really need some help from @ambv to set up a build configuration at the Travis CI server so we can catch errors like these earlier. We've prepared the config file in #166.

[gvanrossum]

I think @ambv has run out of time for this project. Maybe we can convince him to transfer ownership to https://github.com/python/?