Nested task lists

The most organized people know that finishing a task rarely involves just one step. That’s why we’re excited to announce nested task lists!

For example:

- [ ] Figure out wormholes
  - [ ] Call @arfon
  - [ ] Research ([docs](http://en.wikipedia.org/wiki/Wormhole#Time_travel))
  - [ ] Build prototype #15
  - [ ] Test run #43 @world-domination/time-travel
- [ ] ...?
- [ ] Profit!

Now renders as:

Updates work as before: check items on and off to update their completion state.

For more information, see the Writing on GitHub article in the GitHub Help.