Add dependencies for rake and Fluentd

Author: cosmo0920

fluent-plugin-elasticsearch-timestamp-check.gemspec

@@ -13,5 +13,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
+  spec.add_runtime_dependency "fluentd", [">= 0.14.0", "< 2"]
+  spec.add_development_dependency "rake", "~> 11.0"
   spec.add_development_dependency "bundler", "~> 1.3"
 end