Add jscs package and basic conf.

Add [node-jscs](https://github.com/mdevils/node-jscs) package and a basic configuration based on existing [code conventions](https://github.com/MattiSG/Watai/wiki/Code-conventions). 
This configuration needs to be enhanced.

To check the code:

```js
$ npm run lint
```

There are many "Var declarations" errors (multiple `var`). Should be fixed.
There's no reason for the shrinkwrap file to be updated after a developer dependency update. I'd prefer to avoid updating it if it's not needed, to minimize the amount of supported configurations under which to test.