Bump src/dea_next

Bump cloudfoundry/dea_ng:
  Mark Rushakoff:
     upgrade JSON ( Travis Success: https://travis-ci.org/cloudfoundry/dea_ng/builds/16898625 )
     librarian gem is not being used ( Travis Unknown )
  Maria Shaldibina:
     Refactor staging_task_spec to remove before(:all) ( Travis Success: https://travis-ci.org/cloudfoundry/dea_ng/builds/16886603 )
     Remove rcov - not supported in ruby 1.9 ( Travis Success: https://travis-ci.org/cloudfoundry/dea_ng/builds/16741460 )
  Aram Price:
     Instance#promise_link uses Container ( Travis Success: https://travis-ci.org/cloudfoundry/dea_ng/builds/16760152 )
     Add Container#link method ( Travis Unknown )
     Remove redundant log message ( Travis Unknown )
     Move logging statement to reduce duplicate conditional ( Travis Unknown )
     Cleanup comment cruft and spec ordering ( Travis Unknown )
     Fix quotes and spacing ( Travis Success: https://travis-ci.org/cloudfoundry/dea_ng/builds/16757258 )
     Allow ResourceLimits to be optional when calling #spawn ( Travis Unknown )
     Use new Container#resource_limits method to simplify #spawn ( Travis Unknown )
     Move ResourceLimit creation to its own method ( Travis Unknown )
     Simplify Container#spawn ( Travis Unknown )
     Rename for clarity ( Travis Unknown )
     Reformat staging responder ( Travis Success: https://travis-ci.org/cloudfoundry/dea_ng/builds/16745283 )

Signed-off-by: Mark Rushakoff <mrushakoff@pivotallabs.com>