Update Python 3.5 to version 3.5.3. - #172

We seem to be having some issues where https://www.python.org/ftp/python/3.5.3/ is being over-aggressively cached in some places (my office here used to be affected, but appears to be updated now, while our CI server is still affected).

The end result of that over-aggressive caching is that if we merge this now, @docker-library-bot will turn right around and undo the change in a few hours until that cache clears and it sees the update. 😞

So... is it good to go already? :)

Looks like that cache is finally cleared as of today 👍

@tianon Thanks for quick reaction! Can we get the image to show on the Docker Hub - https://hub.docker.com/r/library/python/ ? Python 3.5.3 is still not available there.

We just made a PR to official images docker-library/official-images#2571

See a change merged here that doesn't show up on the Docker Hub yet? Check the "library/python" manifest file in the docker-library/official-images repo, especially PRs with the "library/python" label on that repo. For more information about the official images process, see the docker-library/official-images readme.

- README.md