function invokeArrayArg(arg, fn, context) {
	    if (Array.isArray(arg)) {
	        each(arg, context[fn], context);
	        return true;
	    }
	    return false;
	}
if the argument is an array, we want to execute the fn on each entry
if it aint an array we don't want to do a thing.
this is used by all the methods that accept a single and array argument.
@param {*|Array} arg
@param {String} fn
@param {Object} [context]
@returns {Boolean}