add tunnckoCore/dual-emitter

Very useful micro library for emitting custom and DOM events. https://github.com/tunnckoCore/dual-emitter

> Cross-browser (and IE8) + node.js event emitter. Invoke custom or DOM event. Micro library in 35 lines without jQuery!!!  Useful for two-way data-binding!!

```html
<script>
    var dualEmitter = new DualEmitter();
    var element = document.querySelector('.link');
    dualEmitter
        .on('custom', function(one, two, arr, obj) {
            console.log('test', one, two, arr, obj);
            console.log('------------');
        })
        .on(element, 'click', function(obj, three) {
            console.log('DOM event fired!! Arguments:');
            console.log('first argument', obj);
            console.log('second argument', obj);
        })
        .emit('custom', 1, 2, [3, 4, 5], {six: 'seven'})
        .emit('i:click', {one: 'two'}, 3)
</script>
```