Clarify dogpile.cache differences which occur via #4128.
Clarify dogpile.cache differences which occur via #4128.

The fix for :ticket:`4128` which failed to be included
in the 1.2.5 release also works around an issue in the dogpile.cache
"advanced" example, which will also be fixed independently.

Change-Id: I5eb0da9b93f13f05a8cbe4559e2ed177b1f91a52

monetate/sqlalchemy,graingert/sqlalchemy,wujuguang/sqlalchemy,monetate/sqlalchemy,graingert/sqlalchemy,wujuguang/sqlalchemy,sqlalchemy/sqlalchemy,zzzeek/sqlalchemy,j5int/sqlalchemy,j5int/sqlalchemy