text: Title: xxx.split('/')[-1] may lead to bug when you run eval.py in Windows
  Body: When i first run eval.py just like the Quick Start said:
  >>python ../../tools/eval.py 	 \
  	--tracker_path ./results \ # result path
  	--dataset VOT2016        \ # dataset name
  	--num 1 		 \ # number thread to eval
  	--tracker_prefix 'model'   # tracker_name
  (ps: the argument should be model not 'model', there is no ' ')
  
  i got an error:
  loading VOT2016: 100%|███████████████████████████████████████| 60/60 [00:01<00:00, 49.93it/s, wiper]
  eval ar: 100%|████████████████████████████████████████████████████████| 1/1 [00:00<00:00,  1.97it/s]
  eval eao:   0%|                                                               | 0/1 [00:00<?, ?it/s]multiprocessing.pool.RemoteTraceback: 
  """
  Traceback (most recent call last):
    File "C:\Users\\---\\.conda\envs\pysot\lib\multiprocessing\pool.py", line 121, in worker
      result = (True, func(*args, **kwds))
    File "F:\\---\\pysot-master\toolkit\evaluation\eao_benchmark.py", line 47, in eval
      eao = self._calculate_eao(tracker_name, self.tags)
    File "F:\\---\\pysot-master\toolkit\evaluation\eao_benchmark.py", line 111, in _calculate_eao
      max_len = max([len(x) for x in all_overlaps])
  ValueError: max() arg is an empty sequence
  """
  
  The above exception was the direct cause of the following exception:
  
  Traceback (most recent call last):
    File "../../tools/eval.py", line 147, in <module>
      main()
    File "../../tools/eval.py", line 129, in main
      trackers), desc='eval eao', total=len(trackers), ncols=100):
    File "C:\Users\\---\\.conda\envs\pysot\lib\site-packages\tqdm\std.py", line 1102, in __iter__
      for obj in iterable:
    File "C:\Users\\---\\.conda\envs\pysot\lib\multiprocessing\pool.py", line 748, in next
      raise value
  ValueError: max() arg is an empty sequence
  eval eao:   0%|                                                               | 0/1 [00:00<?, ?it/s]
  
  Finally, i found the cause of this bug. 
    trackers = [x.split('/')[-1] for x in trackers] in File "../../tools/eval.py", line 37, in main()
  This code split tracker name incorrectly. the return value is 'results\\VOT2016\\model' while correct value should be 'model'.
  
  Conclusion: 
  This code should change "x.split('/')" to "x.split('\\')" when you use Windows. Besides, i've not met any other bug caused by this, but i'm not sure that whether the other place uses x.split('/') may lead to bug or not.