chore(package): update ava to version 2.4.0

Closes #15

Author: greenkeeper[bot]

package.json

@@ -42,7 +42,7 @@
     "punchcard-runner": "^2.1.11"
   },
   "devDependencies": {
-    "ava": "^0.16.0",
+    "ava": "^2.4.0",
     "coveralls": "^2.11.15",
     "eslint-config-punchcard": "^1.1.6",
     "ghooks": "^1.3.2",