Adding support for vhost host header (required in Stomp 1.1 protocol)

We recently switched to using Vhosts to segment our queues and I need to use the host header defined in the Stomp 1.1 protocol. 

http://stomp.github.com/stomp-specification-1.1.html#CONNECT_or_STOMP_Frame

I'm actually not that familiar with the Stomp changes for the 1.0 => 1.1 protocol shift. I'd be happy to add them too if you really care to support it. The vhost header was all I needed to get my project back on track after our change in queue management.


i.e.  I am creating my client like this:

````javascript
var client = new stomp.Stomp({
    port: 61613,
    host: 'rmq',
    vhost: 'MY_VIRTUAL_HOST_HEADER',
    debug: true,
});
````