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
The rest of the module works with global variables.  It looks like it would be safe to just use the global `accumulators` here.  Any reason for the discrepancy?  Not that it bothers me much; just curious/checking I'm not missing something.