Add initial implementation of 2-handle range sliders for integers.
Add float implementation of range widget
Add an extended range abbreviation including a step value
Fix format problem when showing an error
Add some tests for the 4-5 int/float form in interact()
Adjust range style so that the vertical range marker is visible
Compiled changes to minified CSS
Remove 4-5 tuple forms from interact()
Fix validate logic if min/max are changed
Remove tests for 4-5 tuples, add tests for validate logic
use momentjs for nice dates
Creating overall structure and organization.
Work on notebook docs.
Working on notebook docs.
Moving over new interact tutorial.
Pulling content from ipython-in-depth.
Remove placement tutorial,
Code will move into styling tutorial
Removed alignment tutorial,
Code will be moved into styleing tutorial
renamed:    Custom Widgets.ipynb -> Date Picker Widget.ipynb
Added widget list