offKeyValue
Unregister an event handler on a MapLike object, based on a key change
    offKeyValue(obj, key, handler, [queueName])
  
  Unregister a handler from the Map-like object obj that had previously been registered with
onKeyValue. The function passed as handler will no longer be called
when the value of key on obj changes.
var obj = new DefineMap({ foo: "bar" });
var handler = function(newVal, oldVal) {
    console.log("foo is now", newVal, ", was", oldVal);
};
canReflect.onKeyValue(obj, "foo", handler);
canReflect.offKeyValue(obj, "foo", handler);
obj.foo = "baz";  // -> nothing is logged
  
  Parameters
- obj 
{Object}:an observable MapLike that can listen to changes in named properties.
 - key 
{String}:the key to stop listening to
 - handler 
{function(*)}:the callback function that should be removed from the event handlers for
key - queueName 
{String}:the queue that the handler was set to receive events from