Lots of updates to 'PURL'

Hey @TheHaverchuck88. We've made lots of changes recently and we decided to call it "Course In a Box" now. You don't have to merge the pull request, but I'd be much obliged if you could have a look and give some feedback. Some of the specific questions I have is:

- Is the fork process too difficult?
- What level of customization should be aim for?
- Are we missing any resources that could help?