Added an upgrading document, with notes about the recent Redis upgrade.
Added an upgrading document, with notes about the recent Redis upgrade.

kaze/paasmaker,paasmaker/paasmaker,kaze/paasmaker,kaze/paasmaker,paasmaker/paasmaker,kaze/paasmaker,paasmaker/paasmaker,kaze/paasmaker,paasmaker/paasmaker,paasmaker/paasmaker