Improve Pyzor client error codes

[alexkiro]

We should improve the pyzor client script to return appropriate error codes when the server is for example unreachable. So the result is easily parsed.

For example in case of timeout, the pyzor script does not output anything:

$ pyzor -d ping
2014-07-21 15:23:14,018 WARNING No accounts are setup.  All commands will be executed by the anonymous user.
2014-07-21 15:23:14,018 DEBUG sending: 'Op: ping\nThread: 63596\nPV: 2.1\nUser: anonymous\nTime: 1405945394\nSig: b9e0f69deb13376b4517911e09f01abd526f39e7\n\n'
2014-07-21 15:23:19,024 ERROR ('127.0.0.1', 24441)  TimeoutError: Reading response timed-out.

Or in case the command is not valid:

$ pyzor -d pign
2014-07-21 15:26:53,056 WARNING No accounts are setup.  All commands will be executed by the anonymous user.
2014-07-21 15:26:53,056 ERROR Unknown command: pign