chore(package): update cross-env to version 6.0.1

Closes #44

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "chai": "^4.1.2",
     "chokidar-cli": "^1.2.0",
     "commitizen": "^2.9.6",
-    "cross-env": "^5.1.3",
+    "cross-env": "^6.0.1",
     "cz-conventional-changelog": "^2.1.0",
     "es6-plato": "^1.0.16",
     "eslint": "^4.17.0",