Add groups function to user object

Useful so that hubot-auth can be used with
[hubot-approval](https://github.com/michaelansel/hubot-approval)

Updated `package.json` so that required hubot version goes from ^2.7.5
to ^2.14.0

package.json

@@ -39,7 +39,7 @@
     "grunt-contrib-watch": "~0.5.3",
     "grunt-mocha-test": "~0.7.0",
     "grunt-release": "~0.6.0",
-    "hubot": "^2.7.5",
+    "hubot": "^2.14.0",
     "hubot-mock-adapter": "^1.0.0",
     "matchdep": "~0.1.2",
     "mocha": "*"

src/auth.coffee

@@ -26,6 +26,10 @@ config =
   admin_list: process.env.HUBOT_AUTH_ADMIN
 
 module.exports = (robot) ->
+  robot.listenerMiddleware (context, next, done) ->
+    context.response.message.user.groups = (cb) ->
+      cb(robot.auth.userRoles(context.response.message.user))
+    next()
 
   unless config.admin_list?
     robot.logger.warning 'The HUBOT_AUTH_ADMIN environment variable not set'