Simplified mechanized release process through tox

fix support for easy_install's find-links option in setup.cfg

Merge pull request #1922 from benoit-pierre/fix_possible_issue_with_transitive_build_dependencies_from_extras

fix possible issue with transitive build dependencies

Rename 'Professional support' to 'For Enterprise' and add section on 'For Enterprise' to the README (linking to Tidelift).

Handle the case where a missing transitive build dependency is
required by an extra for an already installed build dependency.

wheel: fix `is_compatible` implementation

Add new hook 'setuptools.finalize_distribution_options'

Revert "drop easy_install script and associated documentation"

wheel: switch to `packaging.tags` for checking PEP 425 tags

This reverts commit 6e1838a9.

Add support for `license_files` option in metadata

drop easy_install script/command, re-implement `fetch_build_egg` to use pip

Move all finalization of distribution options into hooks. Allow hooks to specify an index for ordering.

tweak workaround for #1644

Work around buggy pip detection code for "pip.exe install/update pip ...".

tests: fix some pytest warnings under Python 2