Add bower to the npm dependencies

flaskbb/themes/aurora/package.json

@@ -7,6 +7,7 @@
   "url": "https://flaskbb.org",
   "private": true,
   "devDependencies": {
+    "bower": "^1.6.9",
     "gulp": "^3.8.11",
     "gulp-bower": "0.0.11",
     "gulp-concat": "~2.4.2",