Remove IndexRoute from ch 06

Index route has not been introduced, and is introduced in ch-8. It seems
both unnecessary and confusing to have it here

lessons/06-params/README.md

@@ -49,7 +49,6 @@ import Repo from './modules/Repo'
 render((
   <Router>
     <Route path="/" component={App}>
-      <IndexRoute component={Home}/>
       <Route path="/repos" component={Repos}/>
       {/* add the new route */}
       <Route path="/repos/:userName/:repoName" component={Repo}/>