fix(package): update fs-extra to version 6.0.0

Author: greenkeeper[bot]

package.json

@@ -21,7 +21,7 @@
     "aggregate-error": "^1.0.0",
     "bottleneck": "^2.0.1",
     "debug": "^3.1.0",
-    "fs-extra": "^5.0.0",
+    "fs-extra": "^6.0.0",
     "globby": "^8.0.0",
     "issue-parser": "^2.0.0",
     "lodash": "^4.17.4",