Ensure the master password is encoded in UTF-8.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Fix breakage on Ruby 1.8.

Ruby 1.8 doesn't know about encodings, so don't call force_encode or encode
on strings.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>