Add heroku node support and try and fix travis

.travis.yml

@@ -1,4 +1,6 @@
-language: python
+language: node_js
+node_js:
+  "6"
 python:
   "2.7"
 

app.json

@@ -46,6 +46,9 @@
     "heroku-postgresql"
   ],
   "buildpacks": [
+    {
+      "url": "heroku/nodejs"
+    },
     {
       "url": "heroku/python"
     }