It doesn't look very good for "native" apps to overscroll when scrolling. Would be nice to have a BrowserWindow option to disable overscroll

![untitled12](https://cloud.githubusercontent.com/assets/170270/15033357/fc36e32e-1293-11e6-8cdc-6c17b0f504dd.gif)
## 
- Electron version: 0.37.8
- Operating system: OS X 10.11.4

atom/renderer/atom_renderer_client.cc
public:
  AtomRenderFrameObserver(content::RenderFrame* frame,
                          AtomRendererClient* renderer_client)
      : content::RenderFrameObserver(frame),
        world_id_(-1),
        renderer_client_(renderer_client) {}
  
  void DidCreateScriptContext(v8::Handle<v8::Context> context,
                              int extension_group,
                              int world_id) override {
    if (world_id_ != -1 && world_id_ != world_id)
      return;
    world_id_ = world_id;
    renderer_client_->DidCreateScriptContext(context);
  }
  void WillReleaseScriptContext(v8::Local<v8::Context> context,
                                int world_id) override {
    if (world_id_ != world_id)
      return;
    renderer_client_->WillReleaseScriptContext(context);
  }
 private:
  int world_id_;
  AtomRendererClient* renderer_client_;
  DISALLOW_COPY_AND_ASSIGN(AtomRenderFrameObserver);
};
}  
AtomRendererClient::AtomRendererClient()