set component state before calling storeDidChange

occasionally, you need to react to store data changing with something other than a component rendering. For these cases there is the `storeDidChange` method. The problem is, when this method fires, the component's `state`has not yet been updated, which is a problem if your `storeDidChange` method needs access to the new data on the store. This fixes that issue by setting the component's `state` before calling the `storeDidChange` method.