build_meta sdist directory delegate to --dist-dir

Revert "Make safe_name compliant to PEP 503 and behaviour of pip > 8.1.2"

Improved handling of  module __path__ attribute for namespace packages, fixes #1321

Make safe_name compliant to PEP 503 and behaviour of pip > 8.1.2

Touch 'egg-info' directory

Pin against sphinx 1.8.0 due to sphinx-doc/sphinx#5417.

build_meta.get_requires_for_build_sdist does not include wheel

Suppress warnings in importer.find_module.

Remove compatibility shim for bytes type

link to setuptools doc

The type bytes is available on all supported Pythons. Makes the code
more forward compatible with Python 3.

the wheel package is not required to build a source distribution

Resolves #1474.