caching sucks

[sersorrel]

when css is updated, it frequently takes a hard-refresh to get the changes to appear (e.g. #197 (comment)). this sucks!

it would be really nice to work out:

• exactly why this happens
• if there's any way we can fix it
• if so, do it; if not, at least write down what the cause is somewhere

[JMAlego]

I think the usual approach to this is adding some form of differentiator to the URL that makes no functional difference but indicates a change to the browser. For example you might have a URL like: https://www.hacksoc.org/static/style_2017.css might become https://www.hacksoc.org/static/style_2017.css?aabbcc123. Then the ID would change when the file did, this works as long as the HTML is updated by the browser (which it is most of the time). A reasonable ID would be the git commit ID or similar.

Not sure if there's a cleaner way than this though...