Creates a Rating Widget React Component

Adds a react rating widget component that allows you to specify a size,
    control hover state, assign an initial rating, supports half stars, and
    can be disabled. Component also has a onRate callback that is called
    when a rating is assigned.

I like to put it this way:

If a method modifies state, modifying state is the only thing it does.

This goes along with the [SOLID Single Responsibility Principle](http://en.wikipedia.org/wiki/SOLID_%28object-oriented_design). I like functions that only do one thing.