Security and privacy enhancements for gnupg's config file for user "user" in /home/user/.gnupg/gpg.conf. See also:  https://raw.github.com/ioerror/torbirdy/master/gpg.conf and https://github.com/ioerror/torbirdy/commit/e6d7c9e6e103f0b3289675d04ed3f92e92d8d7b3.