add reference

ppcls/utils/misc.py

@@ -18,6 +18,7 @@ __all__ = ['AverageMeter']
 class AverageMeter(object):
     """
     Computes and stores the average and current value
+    Code was based on https://github.com/pytorch/examples/blob/master/imagenet/main.py
     """
 
     def __init__(self, name='', fmt='f', postfix="", need_avg=True):