Bump src/gorouter:

Alex Suraci (3):
      switch to yagnats client
      update yagnats
      bump gosteno to fix test

Alex Suraci and David Sabeti (3):
      bump yagnats
      improve logging for invalid json payloads
      bump go_cfmessagebus and yagnats

Alex Suraci and Dennis Schmidt (2):
      add test for stale tracker when state is stale
      fix registry lock when checking nats connectivity

Alex Suraci and Jon Stevens (12):
      force go 1.1 on travis
      force go on travis
      force go 1.1.1 on travis
      remove go-metrics fork
      add Makefile for travis to use
      switch back to go 1.1
      build on go 1.1 and tip (hopefully)
      use .travis.yml install step instead of Makefile
      fix 'go get'
      stop using bin/go and bin/env
      Revert "stop using bin/go and bin/env"
      fix build for Travis's Go 1.1 system