fixes #1510 - notification when host finishes building

![build_complete](https://cloud.githubusercontent.com/assets/429763/4964849/4adf1836-6771-11e4-9410-1324a7373212.png)

Is that meant to essentially read "Foreman build complete"?  It looks like the name is part of the sentence, not a separate heading, so it should be part of the same string or made more separate.