获取iphone的系统信息使用[UIDevice currentDevice],信息如下：
[[UIDevice currentDevice] systemName]：系统名称，如iPhone OS
[[UIDevice currentDevice] systemVersion]：系统版本，如4.2.1
[[UIDevice currentDevice] model]：The model of the device，如iPhone或者iPod touch
[[UIDevice currentDevice] uniqueIdentifier]：设备的惟一标识号，deviceID
[[UIDevice currentDevice] name]：设备的名称，如 张三的iPhone
[[UIDevice currentDevice] localizedModel]：The model of the device as a localized string，类似model