Avoid overlaps with fixed nodes & missing padding

[dbinkele]

Hi,

I have been using the cola.js layouter together with fixed nodes. These are represented as circles. The other ones are rects with some description. The final layout often contains overlaps between those circles and rects.
Between rects there is not such a behavior. But it would be quite beneficial to have some padding around those.
Is there a way to achieve this?

P.S. Thanks for creating this fantastic library!