Remove unused loaders of webpack (#3495)

package.json

@@ -39,8 +39,6 @@
     "babel-preset-env": "^1.4.0",
     "babel-preset-react": "^6.24.1",
     "classnames": "^2.2.5",
-    "coffee-loader": "^0.7.3",
-    "coffee-script": "^1.12.6",
     "compression-webpack-plugin": "^0.4.0",
     "css-loader": "^0.28.1",
     "dotenv": "^4.0.0",
@@ -75,7 +73,6 @@
     "precss": "^1.4.0",
     "prop-types": "^15.5.10",
     "punycode": "^2.1.0",
-    "rails-erb-loader": "^5.0.0",
     "rails-ujs": "^5.1.1",
     "react": "^15.5.4",
     "react-addons-perf": "^15.4.2",