Fix Scrollama problems on browser resize/zoom

[jimjam-slam]

Fixes #101. Based on russellsamora/scrollama#145 (comment)

[jimjam-slam]

Note that I thought I would need to manually reattach the Scrollama event handlers, so I moved them into named functions. I ended up just needing to call .resize() methods on the scroller objects, so the refactor into named functions ended up not being necessary. I think it improves readability and is worth keeping, but I can undo that part if you disagree!

[andrewpbray]

Testing it locally on chrome, the freeze-on-resize issue was still there (as was some jumpiness).

ojs-test.mov

I wanted to test it on the preview site, so I reran that job and, presto, no jumpiness and the resize/reload issue is fixed! Good to know that serving that stuff locally won't behave in quite the same manner.

Alright, I'll proceed with the review!

[andrewpbray]

Small note: in bcfcc66 I moved the second hotkey event listener inside the on-document-load after looking into it a bit a deciding that that probably makes the most sense for all of our listeners.

[andrewpbray]

Looks good!

[jimjam-slam]

I'd originally intended to use this package, but I didn't really want t bite off a bundling toolchain (although we could probably load it via a script tag in the HTML, as we do our existing dependencies). I ended up using the native browser setTimeout() instead, so this can go (although I could try loading it via script and using debounce, which would prevent .resize() being called multiple times). Not sure there's any noticeable performance impact currently, though. I'll remove this commented out code for now.