Should diagnostic thresholds be exposed in the config

[zsusswein]

Or hardcoded in the diagnostic processing. It's easy to expose them, so probably better to just do it?

But we don't really touch them and arguably we'd want to be pretty deliberate about changes, which is an argument for leaving them somewhat buried.

Originally came up in @athowes review on #41.

cc: @kgostic @natemcintosh

[natemcintosh]

Yea, I could see both ways being good. Personally, I have a slight preference for putting them in the config.