Flux todomvc enhancements from justin

2 minor changes:

1. Enable react chrome dev tools.
2. Smaller methods.
Helper methods are often a sign that a block of code could be moved into a new React component, as is the case here.  Helper methods are cool when you are working fast, but an ideal refactor would encapsulate this in another component.  

Like @zpao said, however, we don't need this code to be perfect.  It's really just an introduction to Flux, so I'm not sure if the new component is easier to understand or harder to understand -- this is the point of the example: to make Flux easy to understand.  So I'm inclined to leave it as-is.