Possible race condition with append()

It seems that some kind of race condition can happen. The append of the group isn't propageted to the DOM-tree when "dom.appendTo("#node_" + this.node.label + " .group2");" is called. So I added the group-dom as additional argument to the log-giles render-function.

This is just a quick hack and not fully tested, but it fixed the problem for me.