Fix some this vs. that errors, as well as returning some promises to wait for fulfillment
Fix some this vs. that errors, as well as returning some promises to wait for fulfillment

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