chore(package): update cross-env to version 7.0.0

Closes #126

Author: greenkeeper[bot]

package.json

@@ -21,7 +21,7 @@
   },
   "devDependencies": {
     "body-parser": "^1.14.1",
-    "cross-env": "^5.1.3",
+    "cross-env": "^7.0.0",
     "express": "^4.13.3",
     "flowgen2": "^2.2.0",
     "jest": "^22.1.4",