title: How to update nested store in MobX
body: <p>I've got an App that is wrapped with a Provider.
  Deeper in the App, I'm using a component that's usually is stand alone and has its own Provider. 
  When the "Master" store gets updated, I'd like to pass on the information to the internal store. 
  When I'm doing so, I'm getting a warning from mobx saying - 
  <code>Mobx Provider: Provider store 'internalStore' has changed. Please avoid replacing stores as the change might not propagate to all children</code>.</p>
  
  <p>I can think of two solutions - 
   1. Store the store (internalStore) in the RootStore (pun intended)
   2. Add an update method to the internalStore</p>
  
  <h3>App</h3>
  
  <p><code>
  const App = (props) =&gt; {
      return (
        &lt;Provider store={store}&gt;
          App...
        &lt;/Provider&gt;
      )
  }
  </code></p>
  
  <h3>Internal component -</h3>
  
  <p><code>
  const Internal = (props) =&gt; {
      return (
        &lt;Provider store={internalStore}&gt;
          &lt;ReusedCompoenent /&gt;
        &lt;/Provider&gt;
      )
  }
  </code> </p>
  
  <p>What do you think? Ideas?</p>