add 'benchmark' as dependency

Author: paddor

cztop.gemspec

@@ -26,6 +26,7 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency "czmq-ffi-gen", "~> 1.1", ">= 1.1.0"
 
   spec.add_development_dependency "bundler"
+  spec.add_development_dependency "benchmark"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec"
   spec.add_development_dependency "minitest"