upgrade dev dependencies

Author: tkraak

package.json

@@ -14,7 +14,7 @@
   "author": "",
   "license": "ISC",
   "devDependencies": {
-    "ava": "^0.22.0",
+    "ava": "^0.24.0",
     "nyc": "^11.2.1",
     "snazzy": "^7.0.0",
     "standard": "^10.0.3"