Add a API to stop builds on Jenkins

Sometimes, some builds get stucked on the Jenkins and there is not way to stop these builds without needing to log in on the Jenkins interface and stop they there.

I added an API to stop these stucked builds using hubot.

```
hubot ci stop my_project/123
```

Also, I changed the interface to put explicitly the build on the screen.
![screen shot 2013-06-03 at 20 39 19](https://f.cloud.github.com/assets/47848/602805/7b4b011c-cca7-11e2-81b9-fed4e5767209.png)