Destroy spectrum before removing colorpicker divs

Previously, every time refreshTags was called, sp-container divs
were being left behind. We need to clean those up before removing
the divs that spectrum was initialized with.

public/js/selfoss-base.js

@@ -206,6 +206,7 @@ var selfoss = {
      */
     refreshTags: function(tags) {
         var currentTag = $('#nav-tags li').index($('#nav-tags .active'));
+        $('.color').spectrum('destroy');
         $('#nav-tags li:not(:first)').remove();
         $('#nav-tags').append(tags);
         if(currentTag>=0)