Class Methods
error: 
+ (void)error:(NSString *)format, ...
errorInFunction:withFormat: 
+ (void)errorInFunction:(NSString *)function withFormat:(NSString *)format, ...
info: 
+ (void)info:(NSString *)format, ...
logWithLevel:format: 
+ (void)logWithLevel:(QBLogLevel)level format:(NSString *)format, ...
networkLog: 
+ (void)networkLog:(NSString *)format, ...
setCurrentLevel: 
+ (void)setCurrentLevel:(QBLogLevel)level
setLogBlock: 
+ (void)setLogBlock:(QBLoggerCustomLogBlock)block
warning: 
+ (void)warning:(NSString *)format, ...