Rough draft of slide-only mode feature
Style and improve slide-toggle checkbox
Final color adjustment to checkbox override
Remove slide wrapper/styling on lab include

With the slide toggle feature and spacebar browsing method of slides,
precluding the Lab sections from appear permits a cleaner slide deck
style presentation walkthrough.
Clean up curriculum JS comments, deprecated lines
Merge pull request #242 from github/slide-only-toggle-feature

Slide-only toggle mode for curriculum