Update Flux Dispatcher.dispatch and waitFor examples

The previous examples didn't properly work when 1) a Store callback does
waitFor on Stores that haven't been reached yet and 2) a Store callback
waits on another Store that is already waiting.

The updated example uses constructs Promises up front and then
asynchronously resolves them.
Update todomvc dispatcher to match docs, add AppDispatcher test
Fix doc typo and remove underscore from local var
Configure todomvc-flux npm test to use jest
Add more complicated fourth listener to AppDispatcher-test
Merge pull request #1556 from joshma/flux-dispatcher-docs

Update Flux Dispatcher.dispatch and waitFor examples
Run all tests, fix indentation