aiohttp 2.1.0 release

Changes

• Added support for experimental async-tokio event loop written in Rust
  https://github.com/PyO3/tokio

• Write to transport \r\n before closing after keepalive timeout,
  otherwise client can not detect socket disconnection. #1883

• Only call loop.close in run_app if the user did not supply a loop.
  Useful for allowing clients to specify their own cleanup before closing the
  asyncio loop if they wish to tightly control loop behavior

• Content disposition with semicolon in filename #917

• Added request_info to response object and ClientResponseError. #1733

• Added history to ClientResponseError. #1741

• Allow to disable redirect url re-quoting #1474

• Handle RuntimeError from transport #1790

• Dropped "%O" in access logger #1673

• Added args and kwargs to unittest_run_loop. Useful with other
  decorators, for example @patch. #1803

• Added iter_chunks to response.content object. #1805

• Avoid creating TimerContext when there is no timeout to allow
  compatibility with Tornado. #1817 #1180

• Add proxy_from_env to ClientRequest to read from environment
  variables. #1791

• Add DummyCookieJar helper. #1830

• Fix assertion errors in Python 3.4 from noop helper. #1847

• Do not unquote + in match_info values #1816

• Use Forwarded, X-Forwarded-Scheme and X-Forwarded-Host for better scheme and
  host resolution. #1134

• Fix sub-application middlewares resolution order #1853

• Fix applications comparison #1866

• Fix static location in index when prefix is used #1662

• Make test server more reliable #1896

• Use Forwarded, X-Forwarded-Scheme and X-Forwarded-Host for better scheme and
  host resolution. #1134

• Extend list of web exceptions, add HTTPUnprocessableEntity,
  HTTPFailedDependency, HTTPInsufficientStorage status codes #1920