Adding Sauce Labs testing

Current testing environments: 

```
{ browserName: 'firefox', version: '24' , platform: [ 'Windows 7', 'Linux' ] },
{ browserName: 'internet explorer', version: '10', platform: [ 'Windows 8', 'Windows 7' ] }
```
`npm test` still runs the tests via node only. However Sauce Labs tests run via Travis CI.