Benchmark tooling

[kpcyrd]

It seems some modules perform somewhat poorly. I've suspected this is due to db_insert, but one benchmark investigation that just inserts 1k subdomains finishes in 0.5sec.

The easiest way to tune modules for speed would be a mode that hooks into the http client and returns static responses and writes into a temporary database that is deleted afterwards.

Maybe the proper way to avoid this is just #14 though.