Ability to customize the jshint executable name

For example, one could use jsxhint thanks to this setting.

![linter-configured-with-jshint](https://cloud.githubusercontent.com/assets/55289/3821941/45691062-1d18-11e4-9976-777926dd2f7d.png)

![linter-configured-with-jsxhint](https://cloud.githubusercontent.com/assets/55289/3821940/45685dde-1d18-11e4-9572-45f22361aa32.png)