Revert "Stop using JSX for App component"

This reverts commit 06587de313.

app/components/App.coffee → app/components/App.cjsx

@@ -2,10 +2,9 @@ ThreadSection = require("./ThreadSection")
 MessageSection = require("./MessageSection")
 RouteHandler = Exim.Router.RouteHandler
 
-{div} = Exim.DOM
-
 module.exports = Exim.createView
   render: ->
-    div className="chatapp",
-      ThreadSection()
-      RouteHandler()
+    <div className="chatapp">
+      <ThreadSection />
+      <RouteHandler />
+    </div>