py-tornado: updated to 4.5.3

What's new in Tornado 4.5.3

tornado.curl_httpclient
- Improved debug logging on Python 3.

tornado.httpserver
- Content-Length and Transfer-Encoding headers are no longer
  sent with 1xx or 204 responses (this was already true of 304
  responses).
- Reading chunked requests no longer leaves the connection in a broken
  state.

tornado.iostream
- Writing a memoryview can no longer result in "BufferError:
  Existing exports of data: object cannot be re-sized".

tornado.options
- Duplicate option names are now detected properly whether they use
  hyphens or underscores.

tornado.testing
- .AsyncHTTPTestCase.fetch now uses 127.0.0.1 instead of
  localhost, improving compatibility with systems that have
  partially-working ipv6 stacks.

tornado.web
- It is no longer allowed to send a body with 1xx or 204 responses.

tornado.websocket
- Requests with invalid websocket headers now get a response with
  status code 400 instead of a closed connection.

(adam)