Improve Docs / Error Msg for Protocol Param Syntax

Due to being YAML, the protocol parameters are very sensitive to whitespace (or lack thereof) and other quirks of the standard.

If the entered syntax does not parse correctly, the resulting error message isn't very useful:

```
$ lewis -p "stream:{bind_address:localhost,port:57677}" linkam_t95
2017-10-24 15:55:41,503 INFO lewis.DeviceBase: Creating device, setting up state machine
An error occurred:
'stream:{bind_address:localhost,port:57677}' is not a valid protocol for device 'linkam_t95', select one via the -p option.
Available protocols are:
stream
```

The message should at least suggest that syntax might be the issue.

Also, documentation should do a better job of drawing attention to the fact that this is YAML and whitespace is significant.