Update setup etc. following other projects' example

.gitignore

@@ -49,3 +49,6 @@ htmlcov
 
 # PyCharm
 .idea
+
+sphinx_astropy/version.py
+pip-wheel-metadata/

pyproject.toml

@@ -0,0 +1,5 @@
+[build-system]
+requires = ["setuptools>=30.3.0",
+            "setuptools_scm",
+            "wheel"]
+build-backend = 'setuptools.build_meta'

setup.cfg

@@ -1,26 +1,23 @@
 [metadata]
 name = sphinx-astropy
-version = attr:sphinx_astropy.__version__
 url = https://github.com/astropy/sphinx-astropy
 author = The Astropy Developers
 author_email = [email protected]
 classifiers =
-	Intended Audience :: Developers
-	Programming Language :: Python
-	Programming Language :: Python :: 2
-	Programming Language :: Python :: 3
-	Operating System :: OS Independent
-	License :: OSI Approved :: BSD License
+    Intended Audience :: Developers
+    Programming Language :: Python
+    Programming Language :: Python :: 3
+    Operating System :: OS Independent
+    License :: OSI Approved :: BSD License
 license = BSD
 description = Sphinx extensions and configuration specific to the Astropy project
 long_description = file: README.rst
-
-[bdist_wheel]
-universal = 1
+long_description_content_type = text/x-rst
 
 [options]
 zip_safe = False
 packages = find:
+python_requires = >=3.7
 install_requires =
     sphinx>=1.7
     astropy-sphinx-theme

setup.py

@@ -2,15 +2,9 @@
 
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 
-import sys
-import setuptools
-from distutils.version import LooseVersion
+import os
 from setuptools import setup
 
-# Setuptools 30.3.0 or later is needed for setup.cfg options to be used
-if LooseVersion(setuptools.__version__) < LooseVersion('30.3.0'):
-    sys.stderr.write("ERROR: sphinx-automodapi requires setuptools 30.3.0 or "
-                     "later (found {0})".format(setuptools.__version__))
-    sys.exit(1)
-
-setup()
+setup(
+    use_scm_version={'write_to': os.path.join('sphinx_astropy', 'version.py')}
+)

sphinx_astropy/__init__.py

@@ -1 +1 @@
-__version__ = '1.4.dev0'
+from .version import version as __version__  # noqa