Duplicated logic from `import_requirements()` in requirements.py
to `do_install()` in `install.py` to allow users to specify index
via `--index` command-line option and validate against
`PIP_TRUSTED_HOSTS` when determining `verify_ssl` value.
Update news file to be more descriptive.
* Begin reviewing the basics docs.
* Check in delta
* More doc revisions.
* Split apart basics docs.
* Refactor based on building docs
* add the files back as markdown.
* more conversions to markdown.
* more conversions to markdown.
* fix markdown formatting.
* convert index to markdown.
* More docs review
* More markdown and doc revisions.
* Fix docs.
* Update doc build requirements.
* fix lint
* Fix build with update/upgrade command.
* remove useless quickstart and update the commands section.
* Fix lint
* change ordering of table of contents.
* fix changelog duplicate headings.
* Start splitting advanced topics.
* minor nits
* Move some sections from advanced to shell.
* remove this section as its stale and kind of off topic.
* move scripts out into its own section.
* Wrap up revisions1
* fix lint
* address PR feedback and other nits.
* fix lint
* Try improving ordering of table of contents, fix issue with indexes.md file location.
* fix lint
* PR feedback.
* Split apart core using pycharm refactor move methods.
* move init to remove cicular import.
* Fix imports.
* Check in concept for pipenv upgrade command
* Fix upgrade command expectation on how it updates the lockfile.
* Actually write the result to the Pipfile, and fix secondary bug with items not being written to the Pipfile.
* Fix issue where package being upgraded already exists.
* Add news fragment.
* Integrate upgrade with a refactor of update.
* Handle cases where there is nothing to upgrade.
* Add lock-only option.
* Allow pipenv check inputs to be built from the lockfile categories instead of whats installed.
* fix lint
* add news fragment.
* update pipenv check documentation.
* Revise logic for pipenv check and change default behavior to check lockfile.
* fix issue revealed by tests
* fix docs for pipenv check changes.
* change conditional ordering in prep for supporting for future default categories env var.
Matt Davis