format todomvc example according to todomvc guides.

Hey, feel free to trash this if you had other plans, but I thought I'd quickly adopt the TodoMVC style guides should you guys choose to send a PR our way later. This just points you in the right direction; there are some spec bugs that I didn't attempt to fix, so just [check the app spec](https://github.com/tastejs/todomvc/blob/gh-pages/app-spec.md).

Some of the changes:

- Use Bower for todomvc-common and jQuery
- Tabs instead of spaces
- File re-organization

Sorry that created such an ugly diff :(