Bump lib version so new verify snippets will work

Author: lornajane

package.json

@@ -19,6 +19,6 @@
     "dotenv": "^6.1.0",
     "ejs": "^2.6.1",
     "express": "^4.16.3",
-    "nexmo": "^2.5.1-beta-1"
+    "nexmo": "^2.8.0"
   }
 }