Update dependency eslint to v5

Author: renovate-bot

package.json

@@ -52,7 +52,7 @@
     "babel-preset-react": "6.24.1",
     "codemirror": "5.40.2",
     "css-loader": "0.28.11",
-    "eslint": "4.19.1",
+    "eslint": "5.6.1",
     "eslint-plugin-react": "7.5.1",
     "extract-text-webpack-plugin": "3.0.2",
     "file-loader": "2.0.0",