Fix offsets #38

[miyakelp]

GET my_index/_analyze '{"analyzer":"sudachi_analyzer", "text":["りんご、ごりら", "らっぱ"]}'
{
  "tokens" : [
    {
      "token" : "りんご",
      "start_offset" : 0,
      "end_offset" : 3,
      "type" : "word",
      "position" : 0
    },
    {
      "token" : "ごり",
      "start_offset" : 4,
      "end_offset" : 6,
      "type" : "word",
      "position" : 1
    },
    {
      "token" : "ら",
      "start_offset" : 6,
      "end_offset" : 7,
      "type" : "word",
      "position" : 2
    },
    {
      "token" : "らっぱ",
      "start_offset" : 8,
      "end_offset" : 11,
      "type" : "word",
      "position" : 103
    }
  ]
}

[kazuma-t]

Thank you for your nice patch!