[feature] Cache old results to `~/.cache/pinyin/pinyin.history` and use the old result to fasten

[wzy]

Cache old results to ~/.cache/pinyin/pinyin.history and use the old result to fasten

[Huang Huang]

Thanks for your suggestion. But I'm too busy to do it. Feel free to send a pull request.

IMHO, this feature should be optional and is disabled by default.