- Markdown supported in column description.

- Project > Edit Board and Project Summary pages now show description as tooltip.
- Project > Edit Board shows textarea with markdown preview. Edit column also shows markdown preview.
- Fixed bug while adding a new column inserts description as column limit.

app/Template/board/edit_column.php

@@ -16,7 +16,24 @@
     <?= $this->formNumber('task_limit', $values, $errors) ?>
 
     <?= $this->formLabel(t('Description'), 'description') ?>
-    <?= $this->formTextarea('description', $values, $errors) ?>
+    
+    <div class="form-tabs">
+        <ul class="form-tabs-nav">
+            <li class="form-tab form-tab-selected">
+                <i class="fa fa-pencil-square-o fa-fw"></i><a id="markdown-write" href="#"><?= t('Write') ?></a>
+            </li>
+            <li class="form-tab">
+                <a id="markdown-preview" href="#"><i class="fa fa-eye fa-fw"></i><?= t('Preview') ?></a>
+            </li>
+        </ul>
+        <div class="write-area">
+          <?= $this->formTextarea('description', $values, $errors) ?>
+        </div>
+        <div class="preview-area">
+            <div class="markdown"></div>
+        </div>
+    </div>
+    <div class="form-help"><a href="http://kanboard.net/documentation/syntax-guide" target="_blank" rel="noreferrer"><?= t('Write your text in Markdown') ?></a></div>
 
     <div class="form-actions">
         <input type="submit" value="<?= t('Save') ?>" class="btn btn-blue"/>