Introduce JSCS

* I added [JSCS plugin](https://github.com/jscs-dev/gulp-jscs) to the `lint` task.
* I fixed code styles according to JSCS.
* I introduced [istanbul-coveralls](https://github.com/shinnn/istanbul-coveralls) for coverage reporting.
* I updated [connect](https://github.com/senchalabs/connect), [http-proxy](https://github.com/nodejitsu/node-http-proxy) and [vinyl](https://github.com/wearefractal/vinyl).

(Close #251)