Bump src/collector

Bump cloudfoundry/collector:
  Chris Adams:
     Send a JSON structure for nats ping messages ( Travis created: https://travis-ci.org/cloudfoundry/collector/builds/25723524 )
     Supply a logger to the MessageBus ( Travis Unknown )
  Matthew Sykes:
     Update ruby versions for test and version managers ( Travis Success: https://travis-ci.org/cloudfoundry/collector/builds/25639217 )
  John Foley:
     Merge pull request #9 from yudai/requests/cf_metrics_host_api ( Travis Success: https://travis-ci.org/cloudfoundry/collector/builds/25609377 )
  Iwasaki Yudai:
     Specify host of cf_metrics as URL ( Travis Unknown )

Signed-off-by: Sabha Parameswaran <sparameswaran@gopivotal.com>