Update table_for docs to show method of customization
Update table_for docs to show method of customization

- Note when customization is necessary and when it isn't

mrjman/activeadmin,mrjman/activeadmin,vraravam/activeadmin,activeadmin/activeadmin,javierjulio/activeadmin,mauriciopasquier/active_admin,mrjman/activeadmin,mauriciopasquier/active_admin,vraravam/activeadmin,deivid-rodriguez/activeadmin,mauriciopasquier/active_admin,javierjulio/activeadmin,activeadmin/activeadmin,vraravam/activeadmin,javierjulio/activeadmin,deivid-rodriguez/activeadmin,activeadmin/activeadmin,deivid-rodriguez/activeadmin