Update to Redis 0.25

[brocaar]

Redis 0.25.x has been released. Would it be possible to update deadpool-redis to this version?

It might be needed to make some adaptations (I have not had the time yet to look into this):

use of deprecated method redis::Client::get_async_connection: aio::Connection is deprecated. Use client::get_multiplexed_async_connection instead

Maybe this means that for non-cluster connections, the connection-pool is no longer needed as these queries will use a single multiplexed connection?

[brocaar]

I think a connection pool is still needed, because some queries will block the multiplexed connection, see: redis-rs/redis-rs#851 (comment)

I have made these modifications in my fork:
brocaar@1697c5e

Before creating a pull-request, I will do some local testing first.

[brocaar]

Thanks for reviewing and merging the PR. I think this issue can be closed now :-)