Make closepath commands update current x/y coordinates.

Fixes the following:
```xml
<?xml version="1.0"?>
<svg width="400" height="400" viewBox="0 0 400 400"
     xmlns="http://www.w3.org/2000/svg">
  <path d="m 200,200 100,0 0,100 z l 0,100 -100,0 z m 0,0 -100,0 0,-100 z l 0,-100 100,0 z"
        fill="#cccccc" />
</svg>
```

Which renders incorrectly as
![relative-subpaths](https://cloud.githubusercontent.com/assets/887005/3204634/d800d0d2-edab-11e3-8cf8-47293c61a551.png)

But is supposed to render like
![screen shot 2014-06-06 at 2 00 48 pm](https://cloud.githubusercontent.com/assets/887005/3204713/f536366e-edac-11e3-9fb6-9ce8eac84b47.png)