WIP branch that adds new features from github-book

The demo page loads up.

Some new features:

- Collection can contain tree instead of a list of items
- Dirty Save button is consistent
- Aloha features (dragging things around, new buttons)

There are still some things to clean up:

- [x] merge from `#master`
- [x] remove the dangling references to gh-book (move toc-node, toc-pointer-node, and utils someplace more generic; remove dangling references to binary-file, xhtml-file)
- [x] see if folder editing works
- [x] add back new folders (maybe?)
- [ ] clean up workspace view so it does not show up inside of content pane
- [ ] check that login button appears
- [ ] get remote-changes conflict resolution code working again