add templates support and new flat style option

this adds an option to all badges to do `?style=flat`. you can now also easily add new styles if you wish to support more

![screen shot 2014-04-19 at 1 12 03 am](https://cloud.githubusercontent.com/assets/39759/2747965/705254f6-c79a-11e3-9330-303ea7d1f060.png)