Minimal, portable configuration

Keep shared configuration files lean, portable, and explicit so they work correctly for every contributor and environment. Specifically:

• Do not commit IDE- or machine-specific artifacts (e.g. .idea/*.iml) into the repository. Add them to .git/info/exclude or a local .gitignore instead of checking them in.
• Keep the default/shared config (e.g. setup.cfg) minimal so common commands work out of the box without forcing extra installs. Put optional or environment-specific overrides (e.g. running tests against examples) in the tool that manages variants, such as tox.ini with testpaths = {posargs:tests examples}, rather than hardcoding them in the base config.
• Avoid configuration options tied to a specific legacy tool or VCS (e.g. tag_svn_revision) when a more general, portable option exists (e.g. tag_build/tag_date).
• Make supported environments explicit rather than implicit: declare supported Python versions via python_requires in setup.py, and keep this in sync with documented/tested version support.

Applying these guidelines keeps configuration files predictable, avoids breaking default workflows for other developers, and makes supported environments and dependencies explicit and verifiable.