Explicitly document streams API

[asvetlov]

http://aiohttp.readthedocs.io/en/stable/api.html looks like a piece of garbage.

Especially when I look on streaming API
http://aiohttp.readthedocs.io/en/stable/api.html#module-aiohttp.streams

It mixes native private methods like feed_eof() and feed_data() with decided to be used by top-level programmer like .read_any etc.
Moreover it doesn't suggest to use async for for iterating over incoming data and so on.

The doc should get rid of autodoc usage and switch to explicit documentation writing (as Python itself does).

The far blue sky goal is getting rid of autodoc usage at all for the project.

[lock]

This thread has been automatically locked since there has not been
any recent activity after it was closed. Please open a new issue for
related bugs.

If you feel like there's important points made in this discussion,
please include those exceprts into that new issue.