Use thread pool from concurrent-ruby on ruby server
diff --git a/grpc.gemspec b/grpc.gemspec
index 29d8afe..1b2c553 100755
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -29,6 +29,7 @@
 
   s.add_dependency 'google-protobuf', '~> 3.0.0.alpha.5.0.3'
   s.add_dependency 'googleauth',      '~> 0.5.1'
+  s.add_dependency 'concurrent-ruby'
 
   s.add_development_dependency 'bundler',            '~> 1.9'
   s.add_development_dependency 'facter',             '~> 2.4'