Update to 2.8.21 and 3.0.2

[TimWolla]

see: https://groups.google.com/forum/#!msg/redis-db/4Y6OqK8gEyk/Dg-5cejl-eUJ

A few minutes ago I released Redis 3.0.2 and 2.8.1. The main reason
for this release is to address a security bug found by Ben Murphy,
documented in his blog post here:

http://benmmurphy.github.io/blog/2015/06/04/redis-eval-lua-sandbox-escape/

It is critical but not dramatic: it needs the attacker to have direct
access to the instance, so Redis access mediated by applications is
not at risk. There are a lot of details about vulnerable deployments
in the original blog post.

[tianon]

LGTM