update ruby and gems

Author: rkorzeniec

.ruby-version

@@ -1 +1 @@
-2.1.5
+2.5.8

graphql-preload.gemspec

@@ -22,11 +22,11 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.add_runtime_dependency 'activerecord', '>= 4.1', '< 6'
-  spec.add_runtime_dependency 'graphql', '>= 1.8', '< 2'
-  spec.add_runtime_dependency 'graphql-batch', '~> 0.3'
+  spec.add_runtime_dependency 'graphql', '>= 1.9', '< 2'
+  spec.add_runtime_dependency 'graphql-batch', '~> 0.4'
   spec.add_runtime_dependency 'promise.rb', '~> 0.7'
 
-  spec.add_development_dependency 'bundler', '~> 1.16'
+  spec.add_development_dependency 'bundler', '~> 2.1'
   spec.add_development_dependency 'minitest', '~> 5.0'
   spec.add_development_dependency 'pry', '~> 0.10'
   spec.add_development_dependency 'rake', '~> 10.0'