Add assignment toolbar widgets
Use triple equals, rename to create_assignment
Update preprocessors to work with celltoolbar UI
Update examples
Call the preprocessor in the right place
Style the assignment toolbar better
Better handling of css/extension loading
Add comment about how to load the assignment toolbar
Fix display of points on load/cell type change
Update create assignment example
Update grade assignment example
Merge pull request #8 from jhamrick/celltoolbar

Add nbextensions to help with creating assignments