Add repl to gulp
integrate shorthand
add shorthand tests
Add shorthand test task to npm
integrate coffee-script compiler and esprima
add cell management
Fix typo
Implement 'split cell'
Mouse handling for cell activation.
Prevent default behaviors for enter key in cell input
Implement cell renderers for html, markdown, code syntax highlighting
Improve typography; fix Raw cell rendering
Add cell type preview to all cells
Merge branch 'master' into h2o-flow