For Croogo 1.3.2

Install:
- Put the flattr folder in your app/plugins directory or upload this plugin as a zip in your admin menu
- activate the plugin in admin menu Extensions->Plugins
- change the settings in Extensions->Flattr Settings

Styling:
- The Flattr Button is in a div with the class 'flattr', so style it via css

The Flattr Helper (flattr/views/helpers/flattr.php):
I first coded the FlattrHelper as standalone helper. It still can be used as such and therefore has a lot of comments in it.
So if you are curious, you can read the whole thing. ;)