Update ava to version 0.25.0 (#193)

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
     "yargs": "^11.0.0"
   },
   "devDependencies": {
-    "ava": "^0.24.0",
+    "ava": "^0.25.0",
     "coveralls": "^3.0.0",
     "eslint": "^4.2.0",
     "eslint-config-problems": "0.0.2",