change gem and add preview

app/assets/javascripts/application.js

@@ -21,7 +21,5 @@
 //= require turbolinks
 //= require_tree ../../../lib
 //= require_tree .
-//= require markdown.converter
-//= require markdown.sanitizer
-//= require markdown.editor
+//= require bootstrap_pagedown
 

app/assets/javascripts/markdown_editor.js

@@ -1,19 +1,8 @@
-(function() 
-{
-  var converter = Markdown.getSanitizingConverter();
-  var editor = new Markdown.Editor(converter);
-  editor.run();
-/*  
-	window.MarkdownEditor = function(selector) 
-	{
-    ace.config.set('modePath', ACE_FILES_PATH);
-    var editor = ace.edit($(selector).next()[0]);
-    editor.on('change', function(){ $(selector).val(editor.getValue()); });
-    editor.setShowPrintMargin(false);
-    var session = editor.getSession();
-    session.setMode('markdown');
-    session.setUseWrapMode(true);
-    session.setValue($(selector).val());
- };
- */
-})();
+$(document).ready(function () {
+    var converter = Markdown.getSanitizingConverter();
+    var editor    = new Markdown.Editor( converter );
+
+    Markdown.Extra.init( converter );
+
+    editor.run();
+});

app/assets/stylesheets/application.css

@@ -14,5 +14,5 @@
  *= require_tree ../../../lib
  *= require_tree ../../../vendor/assets/stylesheets/
  *= require_self
- *= require markdown 
+ *= require bootstrap_pagedown
 */

app/views/exercises/_form.html.slim

@@ -9,9 +9,12 @@
   .form-group
     = f.label(:description)
     = f.hidden_field(:description)
+    = f.pagedown_editor :description
+    /.form-control.markdown
     .wmd-panel
-      #wmd-button-bar
+      .wmd-button-bar
       textarea.wmd-input
+      .wmd-preview
     /=f.input :description, :as => :pagedown, :input_html => { :preview => true }
   .form-group
     = f.label(:execution_environment_id)