Return detailed information of token in konoha API

[himkt]

This PR modifies the API server to contain rich token information in a response.

Example

% curl localhost:8000/api/v1/tokenize -X POST -H "Content-Type: application/json" -d '{"tokenizer": "sudachi", "text": "自然言語処理", "with_postag": true}'| jq

{
  "tokens": [
    [
      {
        "surface": "自然",
        "postag": "名詞",
        "postag2": "普通名詞",
        "postag3": "一般",
        "postag4": "*",
        "inflection": "*",
        "conjugation": "*",
        "base_form": "自然",
        "yomi": "シゼン",
        "pron": null,
        "normalized_form": "自然"
      },
      {
        "surface": "言語",
        "postag": "名詞",
        "postag2": "普通名詞",
        "postag3": "一般",
        "postag4": "*",
        "inflection": "*",
        "conjugation": "*",
        "base_form": "言語",
        "yomi": "ゲンゴ",
        "pron": null,
        "normalized_form": "言語"
      },
      {
        "surface": "処理",
        "postag": "名詞",
        "postag2": "普通名詞",
        "postag3": "サ変可能",
        "postag4": "*",
        "inflection": "*",
        "conjugation": "*",
        "base_form": "処理",
        "yomi": "ショリ",
        "pron": null,
        "normalized_form": "処理"
      }
    ]
  ]
}