Rework caching, no longer cache html but cache expensive queries

[cojennin]

First pass at improving #505

Instead of caching the entirety of the html, cache some of the queries that go into building the post details screen (and aren't user dependent). I added about 300 posts to the calendar to check, and there are some small improvements. Have not seen any major performance degradation, though this function now goes uncached.

I'd prefer not to remove the cache in it's entirety without some further investigation, but this PR starts to untangle some of it from the calendar. I've also tried to improve some of the calls being made to other functions to eke out some small performance improvements, and consolidate some calls to functions that didn't seem necessary

Eventually, we could consider doing some things in future PR's like:

1. Limiting the posts that get rendered per day
2. Defer fetching details of a post until a user clicks the post
3. Rendering the initial post information (i.e., title and type) client side

[mjangda]

As discussed, this needs a bit more testing and profiling to see if this is a beneficial change (quick testing shows some benefits).