gae-sessions v1.07 adds thread safety and more

[David Underhill]

gae-sessions 1.07 makes the following improvements:
-- Add support for expiring cookie sessions when the browser closes.
-- Add the Vary header when appropriate (enables users to also use
Django cache middleware).
-- gae-sessions is now thread-safe.
-- Corrupt session is now handled more gracefully.
-- Add set_current_session().

https://github.com/dound/gae-sessions/wiki

Thanks to everyone who contributed patches and made suggestions for
this release!

~ David