asyncio_micro: Rename from asyncio.

As this is not compliant with asyncio API, can't be called asyncio, and
"micro" is just good moniker for what it's intended to be.
asyncio_micro: Work around stupid Python closures.

Which don't close variables, just variable references.
asyncio_micro: StreamReader, StreamWriter: add more methods.
asyncio_micro: Implement start_server().
asyncio_micro: IODone syscall should return to coroutine.
asyncio_micro: Add support for starting a coroutine concurrently.

Just yield it as a value. Also, improve logging/error reporting.
asyncio_micro: Support readall semantics and handle non-blocking read() well.

Non-blocking read()/write() may return None if there's no data, and that's
not EOF.
asyncio_micro: Implement proper write() handling.

TODO: Test!
asyncio_micro: Add basic HTTP server example.