Remove ugliness of checking redis.is_a namespace

Upgrade redis-namspace to latest from git
Upgrade mock_redis to a version that works with newer redis

You wouldn't know it from the diff, but the original bug I'm fixing here is an inconsistency between redis and mock_redis... which leads to an implementation in resque that is completely non-operational in practice

Whenever you try to run a job you'd get

    #<NoMethodError: undefined method `decode' for nil:NilClass>
    /Users/ey/Projects/resque/lib/resque/multi_queue.rb:83:in `block in poll'

Because the blpop call returns the actual Q name (so maybe it could be considered a bug in redis namespace)
And then we search for the Q with the namespace added, and Q resque:resque:queue:default does not exist in real redis. While in mock_redis we'd look for resque:queue:default which does exist.

Updating to the latest redis-namespace (and fixing a completely unrelated mock_redis inconsistency) seems to do the trick