improves template rendering performance

[tgross]

For #643

Reduce the overall rendering time by ~75% via the following:

• cache the entirely-static footer partial
• eliminate looping over all talks in speaker page
• eliminate looping over all speakers in talk page

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This change is 

[bridgetkromhout]

cache the entirely-static footer partial

I'm not sure if I understand entirely how this cache would interact with the Twitter widget in the footer. If the Twitter box can't update until our site builds again, that wouldn't be ideal.

[bridgetkromhout]

eliminate looping over all talks in speaker page
eliminate looping over all speakers in talk page

This is super cool. I want to take a little time with this to make sure I can't break it (muhahaha) and @mattstratton is unavoidably AFK until probably Thursday, but I should be able to get this tested enough to merge before that (and he can do a release after that).

[mattstratton]

Thanks @tgross! This is all so awesome. I’m sure there a lots of examples where I was inefficient. Thank you so much!!

[mattstratton]

cache the entirely-static footer partial

I think that just means the evaluation in the partial isn’t run when building every single page since it’s identical in every single page.

[bridgetkromhout]

Thanks, @tgross! I ran this locally, and you're totally right about the speedup; the currently- code finishes in Total in 101777 ms while this branch finishes in Total in 29991 ms.

And (as expected) it produces the desired results. Hooray!

[tgross]

I'm not sure if I understand entirely how this cache would interact with the Twitter widget in the footer. If the Twitter box can't update until our site builds again, that wouldn't be ideal.

Obviously we've merged this at this point but just in case someone else is reading this: the Twitter widget is client-side in Javascript so we can safely pass the same script to everyone and it'll be up-to-date.