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

Closes #39

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
     "babel-plugin-transform-es2015-modules-umd": "^6.18.0",
     "babel-preset-es2015": "^6.18.0",
     "coveralls": "^3.0.1",
-    "cross-env": "^5.0.0",
+    "cross-env": "^6.0.3",
     "eslint": "^5.0.0",
     "grunt": "^1.0.1",
     "grunt-babel": "^6.0.0",