Fixes missing mkdirp require

Author: alexgorbatchev

package.json

@@ -42,6 +42,7 @@
     "karma-phantomjs-launcher": "^0.2.1",
     "karma-sourcemap-loader": "^0.3.6",
     "karma-webpack": "^1.7.0",
+    "mkdirp": "^0.5.1",
     "mocha": "^2.3.4",
     "node-sass": "^3.4.2",
     "phantomjs": "^1.9.19",