slightly smarter inserting

this adds to the insert logic to try and emulate how badges are included in readmes in the wild

- if a readme is not showing, it uses the current insert point (after the file list)
- if a readme is showing, it inserts the badge after the first child of the readme container
- also removes the text-align center

example:

![screen shot 2014-01-08 at 10 34 02 am](https://f.cloud.github.com/assets/39759/1871210/7a109648-7893-11e3-82a4-22d5fa575b49.png)