Fix jscs integration

The current `jscs` integration does not work due to `jscs/cli` exposing a promise api that was not being taken into consideration. Additionally, `jscs/cli` forces a `process.exit` call which cannot be catched, which means the whole `check-build` script exits. 

I have replaced the usage of the cli by a custom api integration which will open doors for new ideas in the future. As you will see, there is now output from `jscs` and `async` is able to properly pass to the next item in the series. It will also use the default `.jscsrc` file supplied if none is set.

Last, but not least, the code style checks of `jscs` fail for this project :) I do not know if you want to follow the crockford preset if you've defined on the default `.jscsrc` file.