Bump bundler requirements

Author: iloveitaly

hash_diff.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", "~> 1.3"
+  spec.add_development_dependency "bundler", "~> 2.2"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec", "~> 3.1"
 end