packaging: conform to PEP 517 guidelines #519

Problem:
Not compliant with python packaging standards.
Deprecation warnings from pip due to outdated packaging format.
ref #518

Solution:
- Conform to PEP 517 packaging guidelines
- Change packaging and uploading commands in README to allow for building and
  uploading a source distribution as well as a wheel.
- Added language to setup.py to create universal wheel (necessary for continuing
  py2.7 compatibility - even if py2.7 is EOL).
- Add minimal pyproject.toml

.gitignore

@@ -4,10 +4,12 @@ neovim/ui/screen.c
 neovim/ui/screen.so
 build/
 dist/
+venv
 *.pyc
 .cache
 .eggs
 .tox
+.pytest_cache
 
 # Sphinx documentation
 docs/_build/

README.md

@@ -129,8 +129,8 @@ Release
    - bump the version in `pynvim/util.py` and `setup.py` (3 places in total)
 2. Make a release on GitHub with the same commit/version tag and copy the message.
 3. Run `scripts/disable_log_statements.sh`
-4. Run `python setup.py sdist`
+4. Run `python -m build`
     - diff the release tarball `dist/pynvim-x.y.z.tar.gz` against the previous one.
-5. Run `twine upload -r pypi dist/pynvim-x.y.z.tar.gz`
+5. Run `twine upload -r pypi dist/*`
     - Assumes you have a pypi account with permissions.
 6. Run `scripts/enable_log_statements.sh` or `git reset --hard` to restore the working dir.

pyproject.toml

@@ -0,0 +1,3 @@
+[build-system]
+requires = ["setuptools"]
+build-backend = "setuptools.build_meta"

setup.py

@@ -49,4 +49,5 @@
       setup_requires=setup_requires,
       tests_require=tests_require,
       extras_require=extras_require,
-      zip_safe=False)
+      options={"bdist_wheel": {"universal": True}},
+      )