1. Changes travis configuration to use the chrome addon
2. Adds more command line options to runner package
3. Removes grab-headless_shell.sh script
4. Cleans up and adds some environment variables for controlling how
unit tests are ran
5. Fixes a minor issue in chromedp-gen on comment output (for working
with latest protocol definition)
- Added contrib/grab-headless_shell.sh to grab latest headless_shell
- Changed travis config to use contrib/grab-headless_shell.sh
- Reenabled TestStop since Page.stopLoading is now available with latest
available headless_shell