Pass the default worker connection into the started and finished registries

In practice all the registry methods are called with pipelines, but if no
connection is passed in when instantiating the registry and the connection
stack is empty resolve_connection will raise NoRedisConnectionException.
make job description unicode friendly
fix decode
fix decode error in py3.
Merge pull request #438 from adamwen829/master

fix issue #437
Merge pull request #431 from negz/worker-redis-bug

Pass the default worker connection into the started and finished registries