setup rakefile for windows build

gem_rake_helper.rb

@@ -2,7 +2,9 @@ require 'rubygems' unless defined?(Gem)
 require 'rake'
 require 'cucumber/rake/task'
 require 'yard'
-require 'bundler/gem_tasks'
+
+require 'bundler'
+Bundler::GemHelper.install_tasks :name => GEM_NAME
 
 # Skip the releasing tag
 class Bundler::GemHelper

middleman-core/Rakefile

@@ -1,6 +1,8 @@
 # coding:utf-8
 RAKE_ROOT = __FILE__
 
+GEM_NAME = "middleman-core" + (ENV["WINDOWS"] ? "-x86-mingw32" : "")
+
 require 'rubygems'
 require File.expand_path(File.dirname(__FILE__) + '/../gem_rake_helper')
 

middleman-more/Rakefile

@@ -2,4 +2,5 @@
 RAKE_ROOT = __FILE__
 
 require 'rubygems'
+GEM_NAME = "middleman-more"
 require File.expand_path(File.dirname(__FILE__) + '/../gem_rake_helper')

middleman/Rakefile

@@ -2,4 +2,5 @@
 RAKE_ROOT = __FILE__
 
 require 'rubygems'
+GEM_NAME = "middleman"
 require File.expand_path(File.dirname(__FILE__) + '/../gem_rake_helper')