Merge pull request #282 from patrick204nqh/patrick/fix-rack-version-method

Fix Rack 3.x compatibility - Replace `Rack.version` with `Rack.release`

Author: orien

lib/webmachine/adapters/rack.rb

@@ -41,7 +41,7 @@ class Rack < Adapter
       DEFAULT_OPTIONS = {}
 
       REQUEST_URI = 'REQUEST_URI'.freeze
-      VERSION_STRING = "#{Webmachine::SERVER_STRING} Rack/#{::Rack.version}".freeze
+      VERSION_STRING = "#{Webmachine::SERVER_STRING} Rack/#{::Rack.release}".freeze
       NEWLINE = "\n".freeze
 
       # Start the Rack adapter