draggable_component.dart - no 'Selection.node' constructor

[rickbsgu]

Have been using this as a way to learn angular2 - writing an app to display all of these on desktop and mobile.

In both standalone and in the a2 app, the 'Selection.node' constructor is called on lines 71 and 91, and is coming up undefined/not implemented.

[rickbsgu]

Ok, I forked this with the intent to fix it, but it turns out that the actual constructor is 'Selection.elem' rather than 'Selection.node'. Simple fix. There are some other things I think might be worth looking at, so I'll keep the fork up, for now. I'll relay the info here. Right now, I just want to get my demo working....