Bump qunit from 2.5.0 to 2.8.0 (#8)

Bumps [qunit](https://github.com/qunitjs/qunit) from 2.5.0 to 2.8.0.
- [Release notes](https://github.com/qunitjs/qunit/releases)
- [Changelog](https://github.com/qunitjs/qunit/blob/master/History.md)
- [Commits](qunitjs/qunit@2.5.0...2.8.0)

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

package.json

@@ -25,7 +25,7 @@
     "execa": "^0.10.0",
     "get-port": "^3.2.0",
     "prettier": "^1.10.2",
-    "qunit": "~2.6.0",
+    "qunit": "~2.8.0",
     "qunit-eslint": "^2.0.0",
     "rsvp": "^4.7.0"
   },