[iOS7] 改變狀態列文字顏色

1. 增加設置 info plist --> "View controller-based status bar appearance" 為 NO
2. 在AppDelegate.m 裡加上 [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
.......

if (floor(NSFoundationVersionNumber) > NSFoundationVersionNumber_iOS_6_1)
{
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];
}