Merge pull request #457 from KnisterPeter/greenkeeper/execa-0.9.0

Update execa to the latest version 🚀

Author: KnisterPeter

Diff for: package.json

@@ -53,7 +53,7 @@
     "coveralls": "^3.0.0",
     "cz-conventional-changelog": "2.1.0",
     "diff": "3.4.0",
-    "execa": "0.8.0",
+    "execa": "0.9.0",
     "nyc": "11.4.1",
     "prop-types": "15.6.0",
     "react": "^16.0.0",