install ruby, rubygems and ditz

Cygwin 
## ruby をインストール
$ apt-cyg install ruby

## rubygems をインストール
$ mkdir rubygems
$ cd rubygems
$ wget http://rubyforge.org/frs/download.php/57643/rubygems-1.3.4.tgz
$ tar zxvf rubygems-1.3.4.tgz
$ cd rubygems-1.3.4
$ head README
= RubyGems

(See Releases for release-specific information)

== Installation

Get it from RubyForge (http://rubygems.rubyforge.org) and run (as root, if appropriate and necessary)

  ruby setup.rb

$ ruby ./setup.rb
...

## ditz をインストール
$ gem install ditz