Pull changes to collect domain fronting dialing stats

Closes getlantern/lantern#1913  Includes changes that require changes on the Java side, see https://github.com/getlantern/lantern/pull/1921
Nit: just having an array with the thresholds ({2, 4, 8, 16}) would be more readable and flexible.

(Dinner makes me nitpicky, feel free to ignore these. :))