added option to force syntax highlighting language, example: {% include_code file lang:ruby %}. Fixes #108

plugins/include_code.rb

@@ -30,6 +30,10 @@ module Jekyll
     def initialize(tag_name, markup, tokens)
       @title = nil
       @file = nil
+      if markup.strip =~ /\s+lang:(\w+)/i
+        @filetype = $1
+        markup = markup.strip.sub(/\s+lang:\w+\s*/i,'')
+      end
       if markup.strip =~ /(.*)?(\s+|^)(\/*\S+)/i
         @title = $1 || nil
         @file = $3
@@ -52,7 +56,7 @@ module Jekyll
 
       Dir.chdir(code_path) do
         code = file.read
-        @filetype = file.extname.sub('.','')
+        @filetype = file.extname.sub('.','') if @filetype.nil?
         title = @title ? "#{@title} (#{file.basename})" : file.basename
         url = "#{context.registers[:site].config['url']}/#{code_dir}/#{@file}"
         source = "<div><figure role=code><figcaption><span>#{title}</span> <a href='#{url}'>download</a></figcaption>\n"