update example TodoMVC app to use Reflux >= 0.2.1 [fixes #15]

Upgraded Reflux to 0.2.1.

This change required `getInitialState` to be removed from `TodoApp` as it made React to throw the following error:
 
```Invariant Violation: mergeObjectsWithNoDuplicateKeys(): Tried to merge two objects with the same key: list```