Hours per week label

I added an "hours per week label" to the schedule page UI. I figured this would give students an easier and more accurate method of counting up their weekly hours rather than doing it manually. 

Here is a screenshot of the changes I made to the UI:
![newui](https://cloud.githubusercontent.com/assets/6456601/4179941/768239c4-36dd-11e4-9b65-c5f656a19971.png)

Instead of setting the hours per week as a property of the model on initialize, I'd prefer you calculate it on render. In general, keeping extra state around that is derived from other state is an antipattern, because if the original data changes, then you have to make sure to change that derived state too. It is easier to reason about and more functional to simply calculate this value on each render.