Add new API to let people wrap the root component

E.g. for adding Redux support.

lib/intermediate-representation-dir/app.js

@@ -4,26 +4,31 @@ apiRunner('clientEntry')
 
 import React from 'react'
 import ReactDOM from 'react-dom'
-import { AppContainer } from 'react-hot-loader'
+import { AppContainer as HotContainer } from 'react-hot-loader'
 
 const rootElement = document.getElementById(`react-mount`)
 let Root = require('./root')
 if (Root.default) { Root = Root.default }
+
+// Let site, plugins wrap the site e.g. for Redux.
+const NewRoot = apiRunner('wrapRootComponent', { Root: Root }, Root)
 ReactDOM.render(
-  <AppContainer>
-    <Root />
-  </AppContainer>,
+  <HotContainer>
+    <NewRoot />
+  </HotContainer>,
   rootElement
 )
 
 if (module.hot) {
   module.hot.accept(`./root`, () => {
     let NextRoot = require('./root')
     if (NextRoot.default) { NextRoot = NextRoot.default }
+    // Let site, plugins wrap the site e.g. for Redux.
+    const NewRoot = apiRunner('wrapRootComponent', { Root: NextRoot }, NextRoot)
     ReactDOM.render(
-      <AppContainer>
-        <NextRoot />
-      </AppContainer>,
+      <HotContainer>
+        <NewRoot />
+      </HotContainer>,
       rootElement
     )
   })

lib/intermediate-representation-dir/production-app.js

@@ -52,11 +52,15 @@ function shouldUpdateScroll (prevRouterProps, { location: { pathname } }) {
 }
 
 match({ history: browserHistory, routes: rootRoute }, (error, redirectLocation, renderProps) => {
-  ReactDOM.render((
+  const Root = () => (
     <Router
       {...renderProps}
       render={applyRouterMiddleware(useScroll(shouldUpdateScroll))}
       onUpdate={() => {apiRunner('onRouteUpdate', currentLocation)}}
     />
+  )
+  const NewRoot = apiRunner('wrapRootComponent', { Root: Root }, Root)
+  ReactDOM.render((
+    <NewRoot />
   ), typeof window !== `undefined` ? document.getElementById(`react-mount`) : void 0)
 })