Graft Aloha into the editor

**Note:** You will need to build the single-file version of Aloha by running `r.js -o build/aloha/build-profile-with-oer.js` in `bower_components/aloha-editor`.

Done List:

- [x] load Aloha using requirejs
- [x] enable oer block plugins (note, example, exercise)
- [x] add block styling

TODO list (probably demo-able without all of them being checked):

- [ ] move titles out of the `<header>` element
- [ ] update the title's `data-parent-label` when changing block's type via the dropdown
- [ ] add FontAwesome or get the delete/advanced settings buttons visible
- [ ] add jQueryUI for dragging blocks
- [ ] upgrade Bootstrap 2.3.2 (math, image, and link editing depend on this)
- [ ] hide Aloha's floating ribbon toolbar
- [ ] hook toolbar into Aloha
- [ ] serialize the XHTML back into the model
- [ ] dynamically load the Aloha CSS file