chore(package): update fs-extra to version 3.0.0 (#487)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -37,7 +37,7 @@
     "@types/marked": "0.0.28",
     "@types/minimatch": "^2.0.29",
     "@types/shelljs": "^0.7.0",
-    "fs-extra": "^2.0.0",
+    "fs-extra": "^3.0.0",
     "handlebars": "^4.0.6",
     "highlight.js": "^9.0.0",
     "lodash": "^4.13.1",