GH-42 Upgraded bundler dependency.

Author: keithmifsud

jekyll-target-blank.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "jekyll", "~> 3.0"
   spec.add_dependency "nokogiri", "~> 1.10.4"
 
-  spec.add_development_dependency "bundler", "~> 1.6"
+  spec.add_development_dependency "bundler", "~> 2.0"
   spec.add_development_dependency "rake", "~> 12.0"
   spec.add_development_dependency "rspec", "~> 3.0"
   spec.add_development_dependency "rubocop", "0.55"