chore(package): update ava to version 3.3.0

Closes #8

Author: greenkeeper[bot]

package.json

@@ -10,7 +10,7 @@
     "url": "https://github.com/declandewet/pipep/issues"
   },
   "devDependencies": {
-    "ava": "^0.16.0",
+    "ava": "^3.3.0",
     "babel-eslint": "^7.1.0",
     "codecov": "^1.0.1",
     "cross-env": "^3.1.3",