Improve Travis build process

[fallenoak]

We should update Travis to use a more robust build process for Wowser:

1. npm run lint
2. npm test --coverage
3. npm run web-release

Ideally, this will keep Wowser in a much better state for new users to tinker with, as well as keep us more honest about resolving linting complaints.

[timkurvers]

👍