Fix tests

See #63

- Switch from testling to jsdom for browser APIs
- Switch from coverify to nyc for coverage reports
- Clean up related dead code and tooling

.travis.yml

@@ -1,7 +1 @@
 language: "node_js"
-before_script:
-  # testling use headless browser
-  # on travis-ci, firefox is the default one
-  # & it needs a display to works
-  - export DISPLAY=:99.0
-  - sh -e /etc/init.d/xvfb start