Update rack to ~> 1.5.0
Update rack to ~> 1.5.0

This will pull in the latest version of Rack in the 1.5 series

stepri/rack-jekyll,stomar/rack-jekyll,adaoraul/rack-jekyll,pyrasis/rack-jekyll,pyrasis/rack-jekyll,mattr-/rack-jekyll,mattr-/rack-jekyll,adaoraul/rack-jekyll,stepri/rack-jekyll,stepri/rack-jekyll,stomar/rack-jekyll,pyrasis/rack-jekyll