use markdown to render html in email body

app/mailers/room_mailer.rb

@@ -1,12 +1,17 @@
+require 'rdoc/rdoc'
+
 class RoomMailer < ApplicationMailer
 
   def invite
+    formatter = RDoc::Markup::ToHtml.new(RDoc::Options.new, nil)
     @room = Room.find(params[:room_id])
     @user = params[:user]
     @url = params[:url]
+    md = render inline: @room.email_body
+    html = RDoc::Markdown.parse(md).accept(formatter)
     mail(to: "\"#{ @user.name }\" <#{ @user.email }>", subject: @room.email_subject) do |format|
-      # format.html { render 'another_template' }
-      format.text { render inline: @room.email_body }
+      format.html { html }
+      format.text { md }
     end
   end
 end