Update for JupyterLab 0.28
Update for JupyterLab 0.28

SylvainCorlay/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,SylvainCorlay/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,SylvainCorlay/ipywidgets,ipython/ipywidgets,SylvainCorlay/ipywidgets