Drop the first `n` values that are emitted through the stream.
<aside>
```js
//drop(n): Stream
var stream = Rafa.stream();
var values= [];
stream.drop(2).each(v => values.push(v));
stream.enumerate(Rafa.Enumerator.array([1,2,3,4]));
//values: [3,4]
```
</aside>