update sockjs to 0.3.9, websocket-driver to 0.3.4

The websocket-driver update includes our PR to relinquish some memory
faster. https://github.com/faye/websocket-driver-node/pull/6

The sockjs update mostly consists of aligning the version of
faye-websocket it uses internally with the version that we use for our
client. It also contains this Vary: Origin change:
 https://github.com/sockjs/sockjs-node/pull/130