fix(package): update fs-extra to version 6.0.1

Closes #11

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
   "dependencies": {
     "chalk": "^1.1.3",
     "commander": "^2.9.0",
-    "fs-extra": "^4.0.0",
+    "fs-extra": "^6.0.1",
     "image-type": "^3.0.0",
     "read-chunk": "^2.0.0",
     "throat": "^4.0.0",