Modified HostGroups#delete method

Hi Vadv,

I modified HostGroups#delete method so the request looks like

"method": "hostgroup.delete",
"params": [ "42" ]

instead of

"method": "hostgroup.delete",
"params": [ "groupid": "42" ]

which doesn't seem to work as expected as it returns 

 RuntimeError:
       Server answer API error:
        {
         "code": -32500,
         "message": "Application error.",
         "data": "You do not have permission to perform this operation."
       }

I'm using Zabbix 2.0.5.