Comment 4 for bug 1552699

I put together a quick patch to demo this idea (screenshots attached). I think this definitely does a better job showing trends directly since you don't have to mentally combine the two charts, although I think there's still some tweaking to do.

A few areas to improve for sure:
 - opacity is calculated a bit strangely ... I'm sure there's a better way than what I used
 - we'll need to play with period size vs resolution, I think 7 days at hour resolution is too dense?
 - this will need a legend of some sort, it isn't very self explanatory