Bump src/gnatsd

Bump apcera/gnatsd:
  Derek Collison:
     Merge pull request #56 from apcera/fix-coveralls-report ( Travis Success: https://travis-ci.org/apcera/gnatsd/builds/37360126 )
     Merge pull request #53 from mcuadros/master ( Travis Success: https://travis-ci.org/apcera/gnatsd/builds/37226560 )
     Make sure to wait long enough ( Travis Unknown )
  Jonathon Klobucar:
     Travis file was making the coveralls report think everything was master. ( Travis Success: https://travis-ci.org/apcera/gnatsd/builds/37357288 )
  Máximo Cuadros Ortiz:
     fixing http test, disabling keepalive ( Travis Unknown )
     connz: limit and offset ( Travis Unknown )
     added subsz and connz extended, and merged with varz ( Travis Unknown )
     improved connz with subscriptions stats and list of subscriptions by client ( Travis Unknown )
  Julian Friedman and Zach Robinson:
     No longer add subscriptions to router clients with no existing connection. ( Travis Unknown )