Update dependency github-pages to ~> 209

Author: saowang

jekyll-rtd-theme.gemspec

@@ -10,5 +10,5 @@ Gem::Specification.new do |spec|
 
   spec.files         = `git ls-files -z`.split("\x0").select { |f| f.match(%r!^(assets|_layouts|_includes|_sass|LICENSE|README)!i) }
 
-  spec.add_runtime_dependency "github-pages", "~> 207"
+  spec.add_runtime_dependency "github-pages", "~> 209"
 end