Added some correspondence with Conal for my records.
Renamed code to "material". It's not always code.
Fixed typo in slides.
Added new blog post.
Minor edits.
Almost finished "Definition follows meaning" blog post.
Updated material.
Minor changes to "Definition follows meaning"
Only use previously defined properties of cond.

We never expand out its definition.
Updated to Hakyll 4
Remove Hakyll 3 code in comments.