* Move Node tests on Windows to Travis
Appveyor is flaky and can't be restarted by all team members, so moving
everything to Travis is preferable if we can get it to work.
* Actually use latest stable Node
This should also workaround the issue with lts/* not working on
Windows.
* Use npm.cmd instead of raw npm on Windows
* Use p.prettyUri() for Node API tests
Co-authored-by: Natalie Weizenbaum <nweiz@google.com>
