ZKeyChain

Author:
	Kaz Yoshikawa (kyoshikawa@electricwoods.com)

License:
	MIT License
	
Description:	
	Using key chain on iOS is not fun to play.  This class will help
	you access key chain as much like NSMutableDictionary.

Usage:
	
	NSData *someData = ...

	ZKeyChain *keyChain = [ZKeyChian keyChianWithService:@"YourService"];
	[keyChain setString:@"user@domain.com" forKey:@"userid"];
	[keyChain setData:someData forKey:@"data"];
	[keyChain setImage:nil forKey:@"image"];  // remove data from key


API:

	- (void)setData:(id)aData forKey:(NSString *)aKey;
	- (id)dataForKey:(NSString *)aKey;
	- (void)setString:(NSString *)aString forKey:(NSString *)aKey;
	- (NSString *)stringForKey:(NSString *)aKey;
	- (void)setDictionary:(NSDictionary *)aDictionary forKey:(NSString *)aKey;
	- (NSDictionary *)dictionaryForKey:(NSString *)aKey;