1) add plugins and related source files
category_list_tag.rb  -- used to generate category list for sidebar
tag_cloud.rb          -- used to generate tag cloud for sidebar
tag_generator.rb      -- used to generate tag page for post

2) fixbug at .themes/classic/sass/partials/sidebar/_base.scss
when mouse move over sidebar, all <a> link will hilighted with "$sidebar-link-color;"
but the mouse is not over the link