Add style checker to `npm test`

Adding [JSCS](https://www.npmjs.org/package/jscs) with an initially [liberal style check](https://github.com/flightjs/flight/blob/4f610d2e75ac0fd9777795823b87abc3f01ecb27/.jscs.json) to npm test. This will run after the karma tests (including in Travis). The rules can be tightened later if agreed.

Fixed existing code conform to our initial JSCS rules.

I also added a [pre-commit hook](https://github.com/flightjs/flight/blob/4f610d2e75ac0fd9777795823b87abc3f01ecb27/jscs-pre-commit) but for some reason symlinking it to `.git/hooks` did not work - so you may have to copy it there manually