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

Closes #28

Author: greenkeeper[bot]

package.json

@@ -51,7 +51,7 @@
     "babel-preset-env": "^1.7.0",
     "babel-preset-minify": "^0.5.0",
     "chai": "^4.1.2",
-    "cross-env": "^5.2.0",
+    "cross-env": "^6.0.3",
     "eslint": "^5.3.0",
     "eslint-config-airbnb": "^17.0.0",
     "eslint-plugin-import": "^2.13.0",