Bump bundler to v2

Author: mgz

sequel-redshift.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "pg"
   spec.add_dependency "sequel", '~> 5'
 
-  spec.add_development_dependency "bundler", "~> 1.3"
+  spec.add_development_dependency "bundler", "~> 2"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec"
 end