Recommend dependency version management tooling based on use case

Similar to the problem in https://github.com/pypa/python-packaging-user-guide/issues/118 with regards to virtual environment management, our current tooling recommendations don't provide a pointer to higher level dependency version management tools like pipenv or pip-tools, they only refer to pip itself.

While we don't want to overwhelm people with choice, I think we're currently doing folks a disservice by letting them think pip is all there is, rather than guiding them towards more opinionated higher level tooling:

• pipenv: web application development (and potentially other forms of application development)
• pip-tools: general application development (useful when pipenv doesn't align with your needs)
• conda: language-independent cross-platform package (useful when you have extensive external dependencies)

まず、現在のツールに関する推奨事項と、関連する python-packaging-user-guide の issue 118 を読みます。現在 pip がどこで紹介されているかを確認し、そのドキュメントを更新して、読者がユースケースに応じて pipenv、pip-tools、または conda を選べるように案内します。不要な選択肢で読者を圧倒することなく、推奨事項が明確になれば完了です。