Feature/add optional stroke

Added a new feature, you can now choose if you want to have a stroke around the backlight or not.
The default is without a stroke as not to introduce any new default behavior.

You should probably look at the first pull request I made before looking into this was branch out of that pull request.

It looks like this:

![screen shot 2014-10-29 at 22 32 59](https://cloud.githubusercontent.com/assets/57446/4835049/636d6eb8-5fb3-11e4-9ba7-24b07644bad7.PNG)

Hope you like it!