chore(package): update fs-extra to version 8.1.0

Closes #12

Author: greenkeeper[bot]

package.json

@@ -34,7 +34,7 @@
     "async-to-gen": "^1.3.3",
     "execa": "^0.10.0",
     "fixturez": "^1.1.0",
-    "fs-extra": "^5.0.0",
+    "fs-extra": "^8.1.0",
     "husky": "^0.14.3",
     "jest": "^22.1.1",
     "lint-staged": "^7.0.0",