try to get buttons work
Fix arrow-buttons moving left/right cells into base.
Don't obliterate all notebooks. Only process notebooks with nbdiff metadata.
Add logging statements.
change collumn to be column (spelling)
Hide buttons for cells that can't be merged, like 'empty' and 'unchanged'.
Clicking the merge button replaces the base cell.
Adding TODOs
Add extension js file to gruntfile and fix jshint errors.
working on diffing algorithm
Move diff tests to tests/ folder
Merge branch 'master' into diff
find_candidates() works
Adapt find_candidates into an lcs() function
Add another test case for lcs(), make it pass
Write diff_points().
Implement diff()
Fix check_match
Fix create_grid
Remove src directory.