fix(package): update mkdirp to version 1.0.4

Closes #35

Author: greenkeeper[bot]

package.json

@@ -6,7 +6,7 @@
   "dependencies": {
     "dsv": "0.0.x",
     "which": "~1.2.12",
-    "mkdirp": "0.5.x"
+    "mkdirp": "~1.0.4"
   },
   "devDependencies": {
     "istanbul": "~0.4.5",