Django 2.0+: Rewrite `render_to_response()` to `render()`

[dwasyl]

Description

Hey Adam,

Just updating some old code over here and noticed that render_to_response doesn't get seem to get the upgrade treatment to render (and request added as the first arg) so just wanted to flag with hopes it might get added.

[adamchainz]

This is a change from Django 2.0: https://docs.djangoproject.com/en/2.0/releases/2.0/#id1

Fixers for EOL versions are not a priority. I won't put effort into writing them, but PRs are welcome.

This one, in particular, needs extra effort to ensure that a request variable is in scope.