chore(package): update ava to version 3.1.0

Closes #32

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
   ],
   "dependencies": {},
   "devDependencies": {
-    "ava": "^2.3.0",
+    "ava": "^3.1.0",
     "nyc": "^15.0.0",
     "xo": "^0.25.3"
   },