Old Presentations Added

We now have the old presentations uploaded to the DesertPy Presentations Page on the website. This includes Trevor's Mongo presentation, Jerry's RaspberryPi presentation, and my virtualenv and fabric presentations. These presentations, and the source, for some of them are also available on github: https://github.com/desertpy/presentations

This reminds me of the licensing issues we are overlooking while using github. Github is only free for open source, and it is completely my intent to share all of our website and presentation materials under a permissive open source license. I am partial to the three clause MIT/BSD style licenses and that's the route we'll probably follow. We will also need to make sure we get contributors to agree as well. We will formalize this down the road.