title: React: leave the contents of a component alone
body: <p>Is it possible to have React ignore a subtree? i.e., don't compare or update it?</p>
  
  <p>My use case is migrating to React. Re-writing all our Handlebars templates at once isn't feasible, but if we could use our existing templates for some subcomponents, we could adopt it slowly over time.</p>