Don't pulls irrelevant keys out of the data.

I don't have a fix for this yet, but here's a test showing that `process-set-delimiters` is doing something funny. When I use strictly to enforce that bogus keys aren't being retrieved from the map, I see that sometimes the second part of a dotted form is searched for at the top of the map.

This causes me problems because I'd like to use strictly to ensure that I don't inadvertently make inconsistencies between my templates and my data (which allow me to effectively override the silent treatment of nils).

I also wonder if this problem isn't causing other observable effects - though I don't know of any personally.