Implement function to show badges (e.g. Travis-CI)

 Implement the function to add badges into README.md. And POD does not include them (because it is not necessary I think).

Like so;
![minil_badge_sample](https://dl.dropboxusercontent.com/u/14832699/minil_badge.png)


Example of minil.yml in case of the above sample

```yaml
badges = [                                                                                                                                          
    "[![Build Status](https://travis-ci.org/moznion/Plack-Request-WithEncoding.png?branch=master)](https://travis-ci.org/moznion/Plack-Request-WithEncoding)",
    "[![Coverage Status](https://coveralls.io/repos/moznion/Plack-Request-WithEncoding/badge.png?branch=master)](https://coveralls.io/r/moznion/Plack-Request-WithEncoding?branch=master)"
]
```

Could you review this?