Add markdown dialect attribute. (#763)

Resolves #724

examples/markdown/index.html

@@ -120,6 +120,11 @@ are converted to HTML first, then colored by Highlight.js:
   the content was written in simple Markdown.
 </div>
 
+<div class="step slide title markdown" data-rotate="-85" data-x="4000" data-y="2000" data-markdown-dialect="Maruku">
+This is an example of a slide with a specific Markdown dialect.
+===============================================================
+</div>
+
 <script type="text/javascript">
 var enableBwCss = function(){
     disableDevopsCss();