shiritori: return promise

Change-Id: I5b476d3cc4923cb925f07346bd7053f287cd7e84

Author: proppy

functions/index.js

@@ -50,8 +50,8 @@ app.intent('actions.intent.MAIN', (conv) => {
 });
 
 app.intent('actions.intent.TEXT', (conv, input) => {
-  shiritori.loaded.then(() => {
-    shiritori.interact(dict, input, conv.data.used)
+  return shiritori.loaded.then(() => {
+    return shiritori.interact(dict, input, conv.data.used)
         .then(result => {
           conv.data.used.unshift(input);
           conv.data.used.unshift(result.word);