Colorization - color.recurring

- Added support for "color.recurring" configuration variable to
  colorize recurring tasks.
- Updated docs.

html/task.html

@@ -125,6 +125,8 @@
                   <li>Fixed bug that concatenated a modified description without spaces.
                   <li>Added new column 'recur' that displays the recurrence period of any
                       recurring tasks.  This column can be added to any custom report.
+                  <li>Added support for "color.recurring" configuration variable which
+                      specifies the color of recurring tasks.
                 </ul>
 
                 <p>