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

Closes #14

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "yeoman-generator": "^2.0.0"
   },
   "devDependencies": {
-    "fs-extra": "^6.0.0",
+    "fs-extra": "^8.1.0",
     "gulp": "^3.9.0",
     "gulp-coveralls": "^0.1.0",
     "gulp-exclude-gitignore": "^1.0.0",