title: React Context API Seems to re-render every component
body: <p>I'm trying to use the new Context API in my app and it looks like every time I update the context, it re-renders any component connected to it regardless. I have a sandbox demo setup to see code and working issue. When you type in the input - the buttons context is rendered and vice-versa. My original thinking was that if you type in the input, only the input context would be printed out.</p>
  
  <p><a href="https://codesandbox.io/embed/03xpyw1p3l?expanddevtools=1" rel="noreferrer">DEMO</a></p>
  
  <p>Is this how it works or am I missing something?
  Thanks,
  Spencer</p>