don't build docs for auxiliary modules

sinatra-contrib/Rakefile

@@ -7,7 +7,8 @@ task(:test => :spec)
 namespace :doc do
   task :readmes do
     Dir.glob 'lib/sinatra/*.rb' do |file|
-      next if file == 'lib/sinatra/contrib.rb'
+      excluded_files = %w[lib/sinatra/contrib.rb lib/sinatra/capture.rb lib/sinatra/engine_tracking.rb]
+      next if excluded_files.include?(file)
       doc  = File.read(file)[/^module Sinatra\n(  #[^\n]*\n)*/m].scan(/^ *#(?!#) ?(.*)\n/).join("\n")
       file = "doc/#{file[4..-4].tr("/_", "-")}.rdoc"
       Dir.mkdir "doc" unless File.directory? "doc"