Moved widget.js into widget code directory
Added utility function to send all the javascript
in the current directory to the frontend.
Updates to widget.py
Added global init js function
Moved init comm logic to show function
Widget Display logic
Added clear widget area button
Clear widgets upon cell execute
Only create a widget manager when init_widget_js
 is called on the Python side
Adjust weidget box so widget_subarea aligns with codecell
Fab css
Handle widget hide/show logic
also only create a widget manager once
Don't try to load widget.js automatically since it was moved
load using init_widget_js
Add container widget
Add float range widget
Add int range widget
Add selection widget
Add string widget
Register new widgets in IPython.html.widgets namespace