Add Firebase as a dev dependency to satisfy

Author: Jacob Wenger

package.json

@@ -32,6 +32,7 @@
   },
   "devDependencies": {
     "coveralls": "2.11.4",
+    "firebase": "3.x.x",
     "gulp": "3.9.0",
     "gulp-concat": "2.6.0",
     "gulp-ext-replace": "0.2.0",