Keychain-像NSUserDefaults一样使用

就想简单的使用Keychain，不需要Keychain Access Group ，也不需要其他复杂的应用，
就想简单的保存个用户名和密码之类的，
就想像用NSUserDefaults 那样来存储数据。

Methods as follows:

+(BOOL)setObject:(id)object forKey:(NSString *)key;

+(id)objectForKey:(NSString *)key;

+(BOOL)deleteItmeWith:(NSString*)key;

Set Item:

[SimpleKeychain setObject:@"value" forKey:@"key"];

Get Item:

[SimpleKeychain objectForKey:@"key"];

Delete Item:

[SimpleKeychain deleteItmeWith:@"key"];

这是Demo