Move markup_reference.rb into misc directory

The purpose of this change is to leave `doc` directory for RDoc
so that `bundle exec rdoc` inside this repository will work.

Author: okuramasafumi

.gitignore

@@ -14,4 +14,5 @@
 /lib/rdoc/markdown/literals.rb
 /pkg
 /tmp
+/doc
 Gemfile.lock

Rakefile

@@ -24,7 +24,7 @@ RDoc::Task.new do |doc|
   doc.main = 'README.rdoc'
   doc.title = "rdoc #{RDoc::VERSION} Documentation"
   doc.rdoc_dir = '_site' # for github pages
-  doc.rdoc_files = FileList.new %w[lib/**/*.rb *.rdoc doc/rdoc/markup_reference.rb] - PARSER_FILES
+  doc.rdoc_files = FileList.new %w[lib/**/*.rb *.rdoc misc/markup_reference.rb] - PARSER_FILES
 end
 
 task "coverage" do