Svetchine

Hello @julie-ng ! When the graph is updated, the links of the graph are re-rendered, and it triggers the `Graph._bindLayout` method. This method, [only if the webcola engine is selected](https://github.com/julie-ng/newtonjs-graph/blob/master/newton/graph/graph.js#L139)...

By removing the 2 lines here: https://github.com/julie-ng/newtonjs-graph/blob/master/newton/graph/graph.js#L142 https://github.com/julie-ng/newtonjs-graph/blob/master/newton/graph/graph.js#L143 Everything looks fine (graph init and update, even updates with nodes addition and deletion).

Otherwise, but I think you are already aware of this, I believe the problem is located here https://github.com/julie-ng/newtonjs-graph/blob/master/newton/graph/views/links.js#L58. The call to the d3.js selection `data` method [is supposed to identify...