Execution example::

  % curl 'http://localhost:8080/?i=127.0.0.1&l=query&s=93000&q=G&n=query&t=complete&frequency_threshold=1'
  {"complete":[[6],[["_key","ShortText"],["_score","Int32"]],["groonga",3],["g",2],["grooon",2],["gro",2],["groo",2],["gr",2]]}
