Speed up distance for revgeo ranking

Since featureToRequestCenterDistance is a ranking feature, relative values
matter more than absolute. Computing actual earth distance in meters is
expensive as it involves buffering and re-intersecting shapes. Instead, use
Euclidean distance which is much cheaper to compute.

Auditors: nsanch, blackmad
Making warmup multithreaded

Also adding warmup arg to serve.py
Also bumping up twofishes version

Auditors: nsanch, blackmad
bumping up twofishes version
only build 2.10 in travis

Auditors: blackmad
dead code removal

Auditors: blackmad
kill maxCells hint
bump 82.7
force a GC before serving
delete dead code
82.8 bump
more statmons, def -> val cleanup

Auditors: rahul, nsanch
82.9 dead code removal, def -> val, more timings/counters

Auditors: rahul, nsanch
actually reject big radiuses #howdidinotseethis

Auditors: rahul, nsanch
limit max radius to 5km for now

with the new circle code, increasing the radius increases the amount of work you need to do a lot. For now, cap it at 5km because at high neighborhood density, that's about what you can answer in 300ms.

this is a hack that I don't feel great about putting in the public codebase, btu we have so many internal callers that don't sanitize their radius.

Auditors: nsanch, rahul
taiwan aliases