chore(package): update cross-env to version 4.0.0 (#3680)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -53,7 +53,7 @@
     "babel-preset-stage-0": "6.22.0",
     "babel-register": "6.24.0",
     "bcrypt-nodejs": "0.0.3",
-    "cross-env": "3.2.4",
+    "cross-env": "4.0.0",
     "deep-diff": "0.3.4",
     "eslint": "^3.16.1",
     "eslint-plugin-flowtype": "^2.25.0",