Fix query client consensus command

[ancazamfir]

Closes: #286

Description

Added new query parameter for the epoch value.
Running the query against the gaiad/ go relayer setup:

$ rrly -c simple_config.toml query client consensus ibc0 ibconeclient 0 28
    Finished dev [unoptimized + debuginfo] target(s) in 0.15s
     Running `target/debug/relayer -c simple_config.toml query client consensus ibc0 ibconeclient 0 28`
     Options QueryClientConsensusOptions { client_id: ClientId("ibconeclient"), consensus_epoch: 0, consensus_height: 28, height: 0, proof: true }
[relayer/src/chain/cosmos.rs:63] "Todo: implement proof verification." = "Todo: implement proof verification."
client consensus state query result:  Tendermint(ConsensusState { timestamp: Time(2020-10-06T11:06:11.147301Z), root: CommitmentRoot([2, 140, 56, 156, 164, 1, 214, 81, 231, 130, 237, 6, 5, 85, 55, 52, 79, 27, 43, 202, 19, 49, 199, 249, 140, 146, 23, 88, 44, 151, 104, 246]), next_validators_hash: Hash::Sha256(702F9DF2C25EAC1CE7C19DC03E7AA10E3FD9BF1E65EE2A9B96DAEE3DD2E65FC5) })

[romac]

Looks good! Left a suggestion but feel free to ignore it and merge this if you feel it's not worth the change.