Enhancement: stratum.Client should support client.* calls to client from server

[jla415]

example from server to stratum.Client:

{"id": 1289739, "method": "client.get_version", "params": null}.

Currently the library just throws an exception here:

https://github.com/pocesar/node-stratum/blob/c4decc5be6c66173eac7a5ce76de576c9e9a184c/src/client.ts#L151

see: https://en.bitcoin.it/wiki/Stratum_mining_protocol#Methods_.28server_to_client.29

Would be nice to be able to handle and respond to various client.* requests from the server...

[pocesar]

yes, I'm going to cover the new protocol changes, the initial version was using slushpool's in 2013