Added docs for :if options on sidebar and action items

Author: gregbell

docs/7-sidebars.md

@@ -25,6 +25,13 @@ options.
       "Need help? Email us at [email protected]"
     end
 
+If you want to conditionally display a sidebar section, use the :if option and
+pass it a proc which will be rendered within the context of the view.
+
+    sidebar :help, :if => proc{ current_admin_user.super_admin? }
+      "Only for super admins!"
+    end
+
 If you only pass a symbol, Active Admin will attempt to locate a partial to render.
 
     # Will render app/views/admin/posts/_help_sidebar.html.erb

docs/8-custom-actions.md

@@ -92,6 +92,12 @@ post:
       link_to('View on site', post_path(post)) if post.published?
     end
 
+Actions items also accept the :if option to conditionally display them:
+
+    action_item :only => :show, :if => proc{ current_admin_user.super_admin? } do
+      "Only display this to super admins on the show screen"
+    end
+
 ### Page Titles
 
 The page title for the custom action will be the internationalized version of