Foundations Diagram Additions

:warning: WIP :warning: 

Concept diagrams that help visualize basics of Git without any technical labels (commit ref, trees, etc.).

```
![screen shot 2014-05-11 at 10 22 52 pm](https://cloud.githubusercontent.com/assets/352082/2941014/bad597d8-d995-11e3-8599-68a389f0611b.png)
![screen shot 2014-05-11 at 10 22 58 pm](https://cloud.githubusercontent.com/assets/352082/2941016/bad697fa-d995-11e3-8c95-669da6cc7cd2.png)
![screen shot 2014-05-11 at 10 22 55 pm](https://cloud.githubusercontent.com/assets/352082/2941015/bad5d0a4-d995-11e3-8847-de18f4b10eb6.png)
![screen shot 2014-05-11 at 10 23 01 pm](https://cloud.githubusercontent.com/assets/352082/2941017/bad6ad30-d995-11e3-92b3-a3acb4724d40.png)
```