Append an output area using phosphor instead of just DOM elements.
Append an output area using phosphor instead of just DOM elements.

Fixes #670.
cornhundred/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,SylvainCorlay/ipywidgets,jupyter-widgets/ipywidgets,cornhundred/ipywidgets,ipython/ipywidgets,SylvainCorlay/ipywidgets,ipython/ipywidgets,cornhundred/ipywidgets,cornhundred/ipywidgets,SylvainCorlay/ipywidgets,jupyter-widgets/ipywidgets,SylvainCorlay/ipywidgets,cornhundred/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets