Add a reference to the AA mongoid support issue
Add a reference to the AA mongoid support issue

ref: gregbell/active_admin#2714
elia/activeadmin-mongoid,sinsoku/activeadmin-mongoid,SoftwareOps/activeadmin-mongoid,azendoo/activeadmin-mongoid,sinsoku/activeadmin-mongoid,elia/activeadmin-mongoid,azendoo/activeadmin-mongoid,Zhomart/activeadmin-mongoid,elia/activeadmin-mongoid,esobolev/activeadmin-mongoid,devs-for-change/activeadmin-mongoid,activeadmin/activeadmin-mongoid,activeadmin/activeadmin-mongoid,SoftwareOps/activeadmin-mongoid,yaoyi/activeadmin-mongoid,SoftwareOps/activeadmin-mongoid,blotto/activeadmin-parse_resource,devs-for-change/activeadmin-mongoid,esobolev/activeadmin-mongoid,yaoyi/activeadmin-mongoid,azendoo/activeadmin-mongoid,yaoyi/activeadmin-mongoid,esobolev/activeadmin-mongoid,sinsoku/activeadmin-mongoid,devs-for-change/activeadmin-mongoid,Zhomart/activeadmin-mongoid,activeadmin/activeadmin-mongoid,blotto/activeadmin-parse_resource