Feature:
  1. Support comment
    <%# comment %>
  
  2. Support encodeURIComponent
    <%:u=href %>

  3. Support developers custom template function
    app.tpl(template['tpl'], template['data'], {
	fns : {
	    output : 'function(){__p.push.apply(__p, arguments)}'
	}
    })

TODO:
  1. HTML encode
  	<%:h=html %>
  2. unknown