Use optional parameter to set column class

- Fixes the extremely long class name on the post versions view
- Can now use one value instead of having to set th and td
- Added missing column classes on all tables

app/views/users/index.html.erb

@@ -3,7 +3,7 @@
     <h1>Users</h1>
 
     <%= table_for @users, width: "100%" do |t| %>
-      <% t.column do |user| %>
+      <% t.column column: "control" do |user| %>
         <% if CurrentUser.is_admin? %>
           <%= link_to "Edit", edit_admin_user_path(user) %>
         <% end %>