Move RP formatting to Liquid templates

[irisfofs]

Instead of generating the output (oodles and oodles of <p> tags) with Ruby, we could pass the list of LogLines into the page and use a Liquid template to generate the output.

This would let it be more user-configurable, and also use Liquid for what it's meant to do.

[irisfofs]

So this revealed that using Liquid to generate the RP pages is actually really, really slow. Much slower than generating it with Ruby, the previous approach.

It's more expressive and is actually user-editable, but it seems like it might not be worth it.

Reopening this to have the changes moved into their own feature branch, to be potentially readded later.

[irisfofs]

Jekyll 3.1 renders it in around 60% of the time, but it's still very slow.

[irisfofs]

Here's some rough timing, using some "representative sample data" (the collection of 138 RPs currently on my own site):

Jekyll  Liquid  Time
------  ------  ----
v3.1    Yes     23 s
v2.5.3  Yes     37 s
v2.5.3  No       9 s

Also note that using Jekyll v3.1 is currently not supported (see #66). So the options are keep the current, slightly icky Ruby based generation, or multiply build times by 4.

[irisfofs]

The Liquid formatter lives in the feature/liquid-gen-rp-pages branch now. This doesn't necessarily make any sense but that's okay. Could/should maybe have been a tag.