fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-INFLIGHT-6095116

Author: snyk-bot

package.json

@@ -38,18 +38,18 @@
     "chalk": "1.1.3",
     "cross-spawn": "4.0.0",
     "css-loader": "0.23.1",
-    "eslint": "3.1.1",
+    "eslint": "6.0.0",
     "eslint-loader": "1.4.1",
     "eslint-plugin-import": "1.10.3",
     "eslint-plugin-react": "5.2.2",
     "extract-text-webpack-plugin": "1.0.1",
     "file-loader": "0.9.0",
-    "fs-extra": "^0.30.0",
+    "fs-extra": "^1.0.0",
     "html-webpack-plugin": "2.22.0",
     "json-loader": "0.5.4",
     "opn": "4.0.2",
     "postcss-loader": "0.9.1",
-    "rimraf": "2.5.3",
+    "rimraf": "4.0.0",
     "semver": "^5.3.0",
     "style-loader": "0.13.1",
     "url-loader": "0.5.7",