Clarify details on connecting with React (#2527)
Clarify details on connecting with React (#2527)

* Clarify details on connecting with React

1. `VisibleTodoList` has not yet been introduced in the documentation
2. It's slightly confusing to see the combination of a component and container without preamble in a "here's the rest of the code" section.
3. What is a `ref`?

* The App can't be declared until after containers

This breaks the organization of components and containers, but clarifies
the interrelationship between the two. As well as dispels confusion about
whence those two yet-to-be-mentioned containers came.

gaearon/redux,gaearon/redux,roth1002/redux,roth1002/redux,CompuIves/redux,CompuIves/redux