chore(package): update ava to version 1.4.0

Closes #12

Author: greenkeeper[bot]

package.json

@@ -31,7 +31,7 @@
     "node": ">=4"
   },
   "devDependencies": {
-    "ava": "^0.25.0",
+    "ava": "^1.4.0",
     "babel-eslint": "^8.0.0",
     "eslint": "^4.7.2",
     "prettier": "^1.7.0"