Git Town Tutorial

@charlierudolph @allewun 

This adds the beginning of a tutorial. I think this will be helpful to guide newcomers to get faster how Git Town is awesome. I'm not too married to the format and structure, so feel free to comment. This will also be iterated upon a few times later, so the goal here is to get something out that is good enough as a start.

Please let me know what you think!  :)
The point of the tutorial is to walk people step by step through what exactly Git Town does, how it works, and why its awesome. That's why I think its important to explain the steps here. This is especially necessary since the  steps were removed from the command documentation. Also, people who read the tutorial don't know what "syncing" a branch means. Git Town invents that term.