Nested loops on same variable (may) cause inifinite redraws

``` html
<div data-f-foreach="somearray">
   .. stuff --
   <div data-f-foreach="somearray"> </div>
</div>
```

This seems to cause a loop of constant updates as the 'child' asking for the same data as the parent triggers the parent to redraw. 

Fix by implementing something like `shouldComponentUpdate` from React (compare data before re-rendering).
