[Backbone] Course Updates

Thanks for teaching this course at JSConf! I finished up the exercises and found a few small things that needed to be fixed.

I thought I could send an individual pull request for each commit but if that is possible, it's not obvious to me in GitHub's pull request UI, so here they all are (you can ignore my first pull request I sent you, #34). If you don't agree with any let me know and I'll amend it.

Sorry there are some white space fixes in these commits too, I have Sublime Text setup to trim trailing white space whenever I save a file.