Execution example::

  tokenize TokenBigram "日本語の勉強" NormalizerAuto
  # [
  #   [
  #     0, 
  #     1337566253.89858, 
  #     0.000355720520019531
  #   ], 
  #   [
  #     {
  #       "position": 0, 
  #       "force_prefix": false, 
  #       "value": "日本"
  #     }, 
  #     {
  #       "position": 1, 
  #       "force_prefix": false, 
  #       "value": "本語"
  #     }, 
  #     {
  #       "position": 2, 
  #       "force_prefix": false, 
  #       "value": "語の"
  #     }, 
  #     {
  #       "position": 3, 
  #       "force_prefix": false, 
  #       "value": "の勉"
  #     }, 
  #     {
  #       "position": 4, 
  #       "force_prefix": false, 
  #       "value": "勉強"
  #     }, 
  #     {
  #       "position": 5, 
  #       "force_prefix": false, 
  #       "value": "強"
  #     }
  #   ]
  # ]
