make sure students get emails about test failures

[afeld]

Currently, style checks are done through Travis => Grunt => JSHint, but Travis doesn't send any emails to people that aren't Collaborators on the repository, so students end up missing the feedback. Another CI tool may not have this same limitation.

Another option: Hound adds inline comments, which seems like a great way to start conversations if the students have questions, but

• It doesn't have support for HTML validation, though that may not be a huge deal for this class.
• This wouldn't help with automated test failures.
• It wouldn't allow the style config to be centralized via an NPM module, since it needs to be checked in to the repository.

[afeld]

• [x] echo
• [x] countdown
• [x] blink
• [ ] OOP
• [ ] memory
• [ ] mashup