Highlight exit status report strings

Highlight `travis_result` and `travis_wait` message with green (if exit status is 0) and red (otherwise).
![travis_ci_-_free_hosted_continuous_integration_platform_for_the_open_source_community](https://cloud.githubusercontent.com/assets/25666/2543307/f6886ac6-b5f0-11e3-8e4f-b91906c815ac.png)