Merge pull request #61 from pmarsceill/dependabot/bundler/bundler-tw-2.0.1

Update bundler requirement from ~> 1.17.1 to ~> 2.0.1

just-the-docs.gemspec

@@ -16,5 +16,5 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency "jekyll", "~> 3.8.5"
   spec.add_runtime_dependency "rake", "~> 12.3.1"
 
-  spec.add_development_dependency "bundler", "~> 1.17.1"
+  spec.add_development_dependency "bundler", "~> 2.0.1"
 end