add install doc for windows

README.md

@@ -34,6 +34,22 @@ MANUALLY INSTALL
         cd .vim/bundle/command-t/ruby/command-t
         ruby extconf.rb
         make
+
+MANUALLY INSTALL ON WINDOWS
+---------------------------
+
+1. Check out from github
+
+        cd C:\Program Files\Vim   (or the path to Vim)
+        rmdir /s vimfiles         (This deletes your old vim configurations. If you want to keep it, use move instead of rmdir.)
+        git clone git://github.com/vgod/vimrc.git vimfiles
+        git submodule update --init
+
+2. Install vimrc. Add the following line in the end of cd C:\Program Files\Vim\vimrc.
+
+        source $VIM/vimfiles/vimrc
+
+
 
 INSTALL & UPGRADE PLUGIN BUNDLES
 --------------------------------