fix(package): update execa to version 1.0.0

Author: greenkeeper[bot]

package.json

@@ -22,7 +22,7 @@
     "@semantic-release/git": "^7.0.0",
     "@semantic-release/github": "^5.0.0",
     "@semantic-release/npm": "^5.0.1",
-    "execa": "^0.11.0"
+    "execa": "^1.0.0"
   },
   "devDependencies": {
     "ava": "^0.25.0",