Rearrange a require in metadata.rb to break circularity is load.

For some reason this works fine in linux & osx but fails on windows
but only when some things are loaded in isolation. *shrug*

lib/inspec/metadata.rb

@@ -64,6 +64,7 @@ module Inspec
     end
 
     def supports_platform?(backend)
+      require "inspec/resources/platform" # break circularity in load
       backend.platform.supported?(params[:supports])
     end