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.
Some preset rules can be hard to override without just setting `null` and so bypassing them. I don't remember exactly which rules but I already fight some. Anyway. It uses now Google preset with some overrides (`validateIndentation`, `disallowMixedSpacesAndTabs`, `disallowMultipleLineBreaks`).