add jasny offcanvas sidebar

Here's what it looks like with that jasny sidebar off canvas thing that @KHarshawat shared. I'm sharing this here too show y'all what it's like with that tool, although I think there are a couple UI problems with it that we shouldn't use it and probably just use bootstrap media queries. 

UI problems using this:

* When the menu is out, you can't scroll. You need to close the menu before scrolling further. (this makes the scrollspy thing moot). I think it's a result of the jasny bootstrap library and I suspect that jasny sees that as a feature, not a bug. 
* when you open the menu, the main section gets bumped off screen to make space for the sidebar. 

So I think I'll go the route of media queries and stuff, but I wanted to share this in case you wanted to see what it looks like with the off canvas thing.