chore(package): update cross-env to version 6.0.3

Closes #49

Author: greenkeeper[bot]

package.json

@@ -92,7 +92,7 @@
     "colors": "^1.3.2",
     "commitizen": "^3.0.0",
     "coveralls": "^3.0.2",
-    "cross-env": "^5.2.0",
+    "cross-env": "^6.0.3",
     "cz-conventional-changelog": "^2.1.0",
     "http-server": "^0.11.1",
     "husky": "^2.1.0",