Build(deps-dev): Bump qunit from 2.8.0 to 2.9.1 (#34)

Bumps [qunit](https://github.com/qunitjs/qunit) from 2.8.0 to 2.9.1.
- [Release notes](https://github.com/qunitjs/qunit/releases)
- [Changelog](https://github.com/qunitjs/qunit/blob/master/History.md)
- [Commits](qunitjs/qunit@2.8.0...2.9.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

package.json

@@ -25,7 +25,7 @@
     "execa": "^1.0.0",
     "get-port": "^4.0.0",
     "prettier": "^1.10.2",
-    "qunit": "~2.8.0",
+    "qunit": "~2.9.1",
     "qunit-eslint": "^2.0.0",
     "rsvp": "^4.7.0"
   },