chore(package): update mkdirp to version 1.0.4

Closes #80

Author: greenkeeper[bot]

package.json

@@ -21,7 +21,7 @@
     "glob": "^7.1.3",
     "istanbul": "^0.4.5",
     "lolex": "^4.0.1",
-    "mkdirp": "^0.5.1",
+    "mkdirp": "^1.0.4",
     "mocha": "^6.1.3",
     "mocha-headless-chrome": "^2.0.2",
     "npm-check-updates": "^3.1.7",