Move html-webpack-plugin to devDependencies

package.json

@@ -19,7 +19,6 @@
     "es6-promise": "^4.0.5",
     "express": "^4.14.0",
     "firebase": "^3.6.2",
-    "html-webpack-plugin": "^2.24.1",
     "lru-cache": "^4.0.2",
     "serialize-javascript": "^1.3.0",
     "serve-favicon": "^2.3.2",
@@ -37,6 +36,7 @@
     "css-loader": "^0.26.0",
     "extract-text-webpack-plugin": "^2.0.0-beta.3",
     "file-loader": "^0.9.0",
+    "html-webpack-plugin": "^2.24.1",
     "rimraf": "^2.5.4",
     "stylus": "^0.54.5",
     "stylus-loader": "^2.4.0",