chore(package): update @types/fs-extra to version 8.0.0

Closes #76

Author: greenkeeper[bot]

package.json

@@ -79,7 +79,7 @@
     "@types/debug": "0.0.31",
     "@types/download": "6.2.3",
     "@types/express": "4.16.0",
-    "@types/fs-extra": "5.0.4",
+    "@types/fs-extra": "8.0.0",
     "@types/helmet": "0.0.42",
     "@types/js-yaml": "3.11.2",
     "@types/mocha": "5.2.5",