include column position

The position now includes the column number. One thing that still bothers me is that for some node types the range from `start` to `end` includes the whitespace _after_ the actual token. We could remove the trailing `\s*` from the regular expressions and call `whitespace()` after invoking `pos()` but the code would get quite ugly. I think a function that encapsulates both calls would help:

```js
function end(node){
  var ret = pos(node);
  whitespace();
  return ret;
}
```