#2 --keyring e --secret-keyring support

[gian paolo ciceri]

This is a trivial patch to add --keyring and
--secret-keyring support to GnuPGInterface as usable
options.
--
gnupg.options.keyring = "./foo.pub"
gnupg.options.secret_keyring = "./foo.sec"
--
I need them since I've some keys to use that are in a
non-default keyring.
I suppose there's a way in .gnupg/gpg.conf
to have the same effect.

[gian paolo ciceri]

Patch to add --keyring and --secret-keyring support