chore(package): update ava to version 3.1.0

Closes #47

Author: greenkeeper[bot]

package.json

@@ -55,7 +55,7 @@
     "@babel/polyfill": "^7.4.4",
     "@babel/preset-env": "^7.4.5",
     "@babel/register": "^7.4.4",
-    "ava": "^2.1.0",
+    "ava": "^3.1.0",
     "browser-env": "^3.2.6",
     "commitizen": "^3.1.1",
     "conventional-changelog-cli": "^2.0.21",