Fix TypeError when calling $.fn.off() with no args.

jQuery lets you call `off()` with no arguments: http://api.jquery.com/off/#off

It unbinds all event handlers from the element.

This invokes `$.event.remove` with an undefined `types` argument, which caused an error when `jquery.selector-set.js` is loaded:

```
TypeError: Cannot call method 'match' of undefined
    at Object.$.event.remove (file://localhost/Users/dev/projects/jquery-selector-set/jquery.selector-set.js:122:37)
    at HTMLDocument.<anonymous> (http://code.jquery.com/jquery-2.0.3.js:5113:17)
    at Function.jQuery.extend.each (http://code.jquery.com/jquery-2.0.3.js:590:23)
    at jQuery.fn.jQuery.each (http://code.jquery.com/jquery-2.0.3.js:237:17)
    at jQuery.fn.extend.off (http://code.jquery.com/jquery-2.0.3.js:5112:15)
    at Object.<anonymous> (file://localhost/Users/dev/projects/jquery-selector-set/test/test.js:42:15)
```