Respect HTTPServer's no_keep_alive option in RequestHandler.clear.

Also make the keep-alive header check case-insensitive for consistency
with the corresponding code in HTTPServer.

Fixes #31.
Clean up cancelled timeout handles when the queue gets full of them.

Based on a patch by Giampaolo Radola:
https://github.com/facebook/tornado/issues/408

Closes #408.
Remove whitespace/control-character check from RequestHandler.redirect.

Control characters (and newlines and tabs) will be caught in
set_header (which will raise an exception instead of silently
stripping them).  Spaces will now be allowed through, producing
invalid urls, but at least they won't mess up the header framing.

Closes #617.
Release note updates