v2.0.0: Split consume/produce into 2 separate commands (#7)

## Call samples:

### Consume:

`kafkacli -b <broker> consume --pretty-print  <topic1>  <topic1>`

### Produce:

`echo "lol" | kafkacli -b <broker> produce  -H <key>=<value> <topic>`

`cat payload.json | kafkacli -b <broker> produce  -H T<key>=<value> <topic>`

`kafkacli -b <broker> produce  -H <key>=<value> -m="<payload>" <topic>`

## Pretty print
Also, rework the message formatting to (optionally) handle pretty print:

Sample output:

```
---------------- [2019-04-23 17:04:14.687 +0200 CEST]  <topic>/<partition> ----------------
(Headers):
- "Key": "Value"
- "X-Correlation-Id": "7c2cff80-8ea3-4c34-ae72-ef20190be4be"
- "PAYLOAD_TYPE": "TESt"

(Payload):
>big blob of text>
```