Update Rubocop

Author: tas50

sensu-plugins-postgres.gemspec

@@ -53,6 +53,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rake',                      '~> 10.0'
   s.add_development_dependency 'redcarpet',                 '~> 3.2'
   s.add_development_dependency 'rspec',                     '~> 3.1'
-  s.add_development_dependency 'rubocop',                   '0.32.1'
+  s.add_development_dependency 'rubocop',                   '0.34.2'
   s.add_development_dependency 'yard',                      '~> 0.8'
 end