Add documentation about old versions of redis-rb
Add documentation about old versions of redis-rb

hoffmanc/fakeredis,TiteiKo/fakeredis,zegal-cn/fakeredis,alienxp03/fakeredis,alexlag/fakeredis,carsonreinke/fakeredis,gotwalt/fakeredis,caulfield/fakeredis,meetupcall/fakeredis,guilleiguaran/fakeredis