Issue252

I tried to fix issue #252.
And, I fixed the way of getting event data.

Please check the code. And, if there is some problem, let me know.
The result of the function (Using with debug output):
```
[DBG] <JsonParserAgent.cc:187> The index '0' is greater than the size of the array at the current position.
[ERR] <ArmZabbixAPI.cc:384> Error on update: <ZabbixAPI.cc:728> Failed to start element: 0
```

Use following curl:
```
$ curl -d '{"jsonrpc":"2.0","method":"event.get","params":{"output":"extend"},"auth":"<snip>","id":"1"}' -H "Content-Type: application/json-rpc" http://<snip>/zabbix/api_jsonrpc.php

{"jsonrpc":"2.0","result":[],"id":"1"}
```

I'll check it and fix it.