Pubsub client example

[antonshkurenko]

I'm trying to implement ipc pubsub, that's why I tried to check examples on this topic, but I've only found examples for server side (and I know client supports it from #412). Please, give an example also:

1. how to read values from client subscription
2. how to end stream from server side (not using reject method)
3. how to end stream from client side

I see, that jsonrpc uses quite old tokio version, I'm newbie to it, can't find any tutorial on how to do that