Update public/themes/admin/partials/_header.php

Add editor tinyMCE with skin Bootstrap twitter to admin template,
1. - download the latest TinyMCE package from 
     http://www.tinymce.com/download/download.php
   - Unzip put the folder "tiny_mce" from tinymce/jscripts/ to the admin theme path 
     (./bonfire/themes/admin/js/) and put the css file "content.css"
     from tinymce/examples/css/ to ./bonfire/themes/admin/css/tinymce/

download the skin from :
- https://github.com/gtraxx/tinymce-skin-bootstrap
- unzip and put to admin theme path (./bonfire/themes/admin/js/tiny_mce/themes/advanced/skins) 

put this script bitween <head> tag or you can put in global.js
<script src="<?php echo Template::theme_url('js/tiny_mce/tiny_mce.js'); ?>"></script>

	<script type="text/javascript">
	    tinyMCE.init({
	       // General options
	       mode : "textareas",
	       theme : "advanced",
	       skin : "bootstrap",
	       plugins : "table,inlinepopups",
	       // Theme options
	       theme_advanced_buttons1 : "save,newdocument,|,bold,italic,underline,strikethrough,|,justifyleft,justifycenter,justifyright,justifyfull,|,styleselect,formatselect,fontselect,fontsizeselec",
	       theme_advanced_buttons2 : "cut,copy,paste,pastetext,pasteword,|,search,replace,|,bullist,numlist,|,outdent,indent,blockquote,|,undo,redo,|,link,unlink,anchor,image,cleanup,help,code,|,insertdate,inserttime,preview,|,forecolor,backcolor",
	       theme_advanced_buttons3 : "tablecontrols,|,hr,removeformat,visualaid,|,sub,sup,|,charmap,emotions,iespell,media,advhr,|,print,|,ltr,rtl,|,fullscreen",
	       theme_advanced_buttons4 : "insertlayer,moveforward,movebackward,absolute,|,styleprops,spellchecker,|,cite,abbr,acronym,del,ins,attribs,|,visualchars,nonbreaking,template,blockquote,pagebreak,|,insertfile,insertimage",
	       theme_advanced_toolbar_location : "top",
	       theme_advanced_toolbar_align : "left",
	       theme_advanced_statusbar_location : "bottom",
	       theme_advanced_resizing : true,
	       // Example content CSS (should be your site CSS)
	       content_css : "<?php echo Template::theme_url('css/tinymce/content.css'); ?>"
	    });
    </script>

Thank's to gtraxx (https://github.com/gtraxx/)