fix(package): update fs-extra to version 9.0.0

Closes #26

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "d3-node": "^1.1.3",
     "debug": "^3.1.0",
     "fast-csv": "^2.4.1",
-    "fs-extra": "^6.0.1",
+    "fs-extra": "^9.0.0",
     "microtime": "^2.1.6",
     "mkdirp-promise": "^5.0.1",
     "moment": "^2.20.1",