jshint should lint the tests directory by default

[tomconnell-wf]

I was surprised when wGulp did not lint my specs. My expectation came from using wf-grunt, were I believe tests are linted by default. I think it is probably a happy default to test specs, because with a bad enough syntax error, jasmine will silently not run the spec file. CI could succeed with a whole suite of tests broken. That would be bad. I don't think there are large downsides to linting unit tests. Maybe people don't want style enforced on tests?

Here's a quick hack of how to maybe do it. #128