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

Closes #63

Author: greenkeeper[bot]

package.json

@@ -44,7 +44,7 @@
     "chai": "^4.2.0",
     "chai-as-promised": "^7.1.1",
     "coveralls": "^3.0.9",
-    "cross-env": "^5.1.3",
+    "cross-env": "^7.0.0",
     "fs-extra": "^5.0.0",
     "globule": "^1.2.1",
     "hard-rejection": "^2.1.0",