subscribeOnScope promise does not return subscription

[kryo2k]

https://github.com/voryx/angular-wamp/blob/master/src/angular-wamp.js#L399-L401

Suggesting to add:

return subscription;

Currently promise returns undefined. I worked around this with an extension of that method.

Patched:

subscribeOnScope: function (scope, channel, callback) {
    return this.subscribe(channel, callback).then(function (subscription) {
        scope.$on('$destroy', function () {
            return subscription.unsubscribe();
        });
        return subscription;
    });
},

[bondt]

@davidwdan Thanks! @kryo2k Tested and works. Can you verify?

[davidwdan]

Fixed https://github.com/voryx/angular-wamp/pull/51