Bump src/collector

Bump cloudfoundry/collector:
  Joseph Rodriguez:
     Merge pull request #12 from jmtuley/master ( Travis Success: https://travis-ci.org/cloudfoundry/collector/builds/30788629 )
     Report Metron metrics [#75479224] ( Travis Unknown )
  Zach Robinson:
     Update nats.ping format ( Travis Success: https://travis-ci.org/cloudfoundry/collector/builds/30693124 )
  Graeme Davison and Joseph Palermo:
     Add code coverage badge to readme ( Travis Success: https://travis-ci.org/cloudfoundry/collector/builds/30502839 )
     Add code coverage ( Travis Success: https://travis-ci.org/cloudfoundry/collector/builds/30502756 )

Signed-off-by: Joseph Rodriguez <jrodriguez@pivotallabs.com>