tornado.web.RequestHandler.set_header now properly sanitizes input
values to protect against header injection, response splitting, etc.
(it has always attempted to do this, but the check was incorrect).
Note that redirects, the most likely source of such bugs, are protected
by a separate check in .RequestHandler.redirect.
Colored logging configuration in tornado.options is compatible with
Python 3.2.3 (and 3.3).