chore(package): update @semantic-release/exec to version 3.3.1

Closes #22

Author: greenkeeper[bot]

package.json

@@ -10,7 +10,7 @@
   "license": "WTFPL",
   "devDependencies": {
     "@semantic-release/changelog": "^2.0.1",
-    "@semantic-release/exec": "^2.2.3",
+    "@semantic-release/exec": "^3.3.1",
     "@semantic-release/git": "^4.0.1",
     "@semantic-release/github": "^4.2.8",
     "@semantic-release/npm": "^3.2.4",