Pin exactly futures-0.2.0-beta.

Tokio does not support stable futures 2 yet

Bump tokio-zmq-derive

Update to work with latest futures, tokio

Merge pull request #9 from asonix/0.3.x

0.3.x

Don't let TimeoutStreams be created if they won't implement Stream

oops

Bump version

bump version

Merge branch 'master' of github.com:asonix/tokio-zmq

Add documentation