chore(package): update ava to version 1.2.0

Closes #42

Author: greenkeeper[bot]

package.json

@@ -19,7 +19,7 @@
     "when": "^3.7.7"
   },
   "devDependencies": {
-    "ava": "^0.20.0",
+    "ava": "^1.2.0",
     "coveralls": "^2.13.1",
     "nyc": "^11.0.3",
     "source-loader": "^0.2.0",