More modes of operation

Updates the ciphers to support GCM, OFB8 and OFB1 modes, GCM is available in version 0.10 of node, but it's not actually usable until version 0.11 where methods for getting/setting the tags where added, it's probably a good idea to get that in here earlier rather then latter as its the default cipher mode for tls in verison 0.11