[WIP] Hash-based comparison for weak compare

[ltclever]

an attempt to make weak compare faster

a little hacky. to be tested.

[ltclever]

cc @Christopher-Bradshaw @drhurd @samfishman

[ltclever]

ran a correctness job with weak compare enabled on permissions service (which sees array reordering)

standard recursive compare (master branch) results:

2016/11/01 20:10:02 Results map[int]map[int]int{},
2016/11/01 20:10:02 0 Diffs using weak compare: true,
{"control_url":"https://ltc--permissions-service.int.clever.com:443",
"deploy_env":"ltc-hs",
"diffs":0,
"exp_url":"https://ltc-exp--permissions-service.int.clever.com:443",
"last_gorfile":"/tmp/prod-replay-testing-permissions-service-1-2016-11-01-17-01-40-56f4d9d8-9654-458f-b178-89ff1c99818a.txt",
"level":"info",
"load_url":"",
"reqs":2122,
"source":"http-science",
"title":"progress"},
2016/11/01 20:10:02 2122 reqs in 35m14.470129024s seconds

[Christopher-Bradshaw]

I've also found running it with some intentional diffs a useful sanity check.