remove data-set dependency

i'm wondering if you're interested in removing this to reduce the dependencies.  this can be achieved using a higher order function and leveraging a property value that is a function.

```js
function dataset(value) {
  return function (node, propName) {
    require('data-set')(node)[propName] = value;
  };
}

h('div', {
   prop: dataset('value')
});
```