First Try

This my first time trying a pull request. I was curious to know if this would update the course materials for me. I also attached my ER diagrams from chapter 4
![music db er diagram](https://f.cloud.github.com/assets/3334076/241409/2fde1ed8-89ab-11e2-834e-be58f8bb9a2c.png)
![online media store](https://f.cloud.github.com/assets/3334076/241411/32b1c862-89ab-11e2-804d-8f6544d7d1f5.png)