py-aiohttp: updated to 3.1.0

3.1.0:

Features
- Relax JSON content-type checking in the ClientResponse.json() to allow
  "application/xxx+json" instead of strict "application/json".
- Bump C HTTP parser to version 2.8
- Accept a coroutine as an application factory in web.run_app and gunicorn
  worker.
- Implement application cleanup context
- Make writer.write_headers a coroutine.
- Add tracking signals for getting request/response bodies.
- Deprecate ClientResponseError.code in favor of .status to keep similarity
  with response classes.
- Implement app.add_routes() method.
- Implement web.static() and RouteTableDef.static() API.
- Install a test event loop as default by asyncio.set_event_loop(). The
  change affects aiohttp test utils but backward compatibility is not broken
  for 99.99% of use cases.
- Refactor ClientResponse constructor: make logically required constructor
  arguments mandatory, drop _post_init() method.
- Use app.add_routes() in server docs everywhere
- Websockets refactoring, all websocket writer methods are converted into
  coroutines.
- Provide Content-Range header for Range requests

Bugfixes
- Fix websocket client return EofStream.
- Fix websocket demo.
- Property BaseRequest.http_range now returns a python-like slice when
  requesting the tail of the range. It's now indicated by a negative value in
  range.start rather then in range.stop
- Close a connection if an unexpected exception occurs while sending a request
- Fix firing DNS tracing events.

Improved Documentation
- Change ClientResponse.json() documentation to reflect that it now
  allows "application/xxx+json" content-types
- Document behavior when cchardet detects encodings that are unknown to Python.
- Add diagrams for tracing request life style.
- Drop removed functionality for passing StreamReader as data at client
  side.


(adam)