minio: Output server logs & startup in json format

Currently minio logs with enhanced tty data and journalctl does not include anything useful as a result:

```
Jun 08 11:03:28 alpha minio[17813]: [78B blob data]
Jun 08 11:03:28 alpha minio[17813]: [49B blob data]
Jun 08 11:03:28 alpha minio[17813]: [19B blob data]
Jun 08 11:03:28 alpha minio[17813]: [88B blob data]
Jun 08 11:03:28 alpha minio[17813]: [45B blob data]
Jun 08 11:03:28 alpha minio[17813]: [44B blob data]
Jun 08 11:03:28 alpha minio[17813]: [57B blob data]
```

Indicating that it detected some binary output.  With the `--json` flag it logs:

```
Jun 08 11:14:58 alpha minio[18573]: {"level":"FATAL","time":"2018-06-07T23:14:58.770637778Z","error":{"message":"--address input is invalid: address 127.0.0.1: missing port in address","source":["/build/go/src/github.com/minio/minio/cmd/server-main.go:121:cmd.serverHandleCmdArgs()"]}}
```