fix(package): update react-hot-loader to version 4.12.18

Closes #21

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "prop-types": "^15.6.0",
     "react": "^16.2.0",
     "react-dom": "^16.2.0",
-    "react-hot-loader": "^3.1.3",
+    "react-hot-loader": "^4.12.18",
     "react-icons": "^2.2.7",
     "react-reveal": "^1.2.1",
     "react-router-dom": "^4.2.2",