Add price field to studio and logic to show/hide price

@stvstnfrd & @jbau 

Screenshots to give a better idea of functionality:

Set "Course Price" in studio:
![screen shot 2014-10-14 at 11 19 37 am](https://cloud.githubusercontent.com/assets/3364609/4634338/4edd0520-53cf-11e4-98ee-d754688567f5.png)



"Course Price" is displayed on About Page:
![screen shot 2014-10-14 at 11 22 04 am](https://cloud.githubusercontent.com/assets/3364609/4634345/5d354e7a-53cf-11e4-90e6-032c0b78427a.png)

Remove trailing whitespace here.

Actually, I think I've noticed this on your last several PRs. Could you:
- update your text editor's settings to remove or not insert trailing
  whitespace
- and/or
- review diffs before committing and then explicitly stage changes with
  `git add --patch` so that you aren't accidentally committing unrelated
  changes

Doing the former will prevent most of these kinds of things, but the
latter is pretty useful too.