Disabling physics

[Robrechtc]

Hey Andrei!

I've been playing around with ngraph for a while but we've got some issues with the physics. I read the issues on VivaGraphJS and you mentioned pinning the center node but I haven't managed to recreate it. There are two things that we would really like to change: the graph moving outside of the screen and the "wobble". I found and looked at ngraph.forcelayout as well as ngraph.physics.simulator, but trying to include it in my script with the example code provided didn't do anything. https://dpaste.de/wdQ6 this is my script, everything has the proper path provided this time :p for the physics numbers, I just changed them a bit from what's on ngraph.forcelayout but I didn't see any changes. Again, many thanks for your help and I love the framework you've created here!