a few changes to make A/B testing easier

app/routes/download.js

@@ -0,0 +1,9 @@
+const preview = require('../templates/preview');
+const download = require('../templates/download');
+
+module.exports = function(state, emit) {
+  if (state.transfer) {
+    return download(state, emit);
+  }
+  return preview(state, emit);
+};