Added DietPi image (thibmaek#26)

* Added DietPi image

- Small, designed to fit 2GB SD cards
- Auto-expands to full size of SD card on boot
- Lots of pre-boot editable settings (can be modified on Windows, even)
- Lots of configurable scripts, equally as easy to set up

Only image I use, now.

* Update README.md

Author: JarrettR

README.md

@@ -35,6 +35,7 @@ Contributions *very welcome* but first see [Contributing](#contributing)
 * [Lakka](http://lakka.tv) - Retro-gaming on the Raspberry Pi built entirely on RetroArch.
 * [RasPlex](http://www.rasplex.com/) - A Plex client for the Raspberry Pi.
 * [chilipie-kiosk](https://github.com/futurice/chilipie-kiosk) - Image which boots directly into full-screen Chrome, perfect for dashboards and build monitors. ![Supports Raspberry Pi 2+](/media/badges/rpi-2+.png)
+* [DietPi](https://github.com/Fourdee/DietPi) - Mimimal image designed to fit on a 2GB SD card, with tons of configurable settings and scripts.
 
 # Tools
 * [PiBakery](http://www.pibakery.org/) - The blocks based, easy to use setup tool for Raspberry Pi.