Revert "Remove setup.py to fix Heroku deploy."

This reverts commit 88bf02b586.

It also should fix documentation building.

setup.py

@@ -0,0 +1,26 @@
+from setuptools import find_packages, setup
+
+setup(
+    name='mozilla-atmo',
+    use_scm_version=True,
+    setup_requires=['setuptools_scm'],
+    packages=find_packages(exclude=['tests', 'tests/*']),
+    description='The code of the Telemetry Analysis Service',
+    author='Mozilla Foundation',
+    author_email='telemetry-analysis-service@mozilla.org',
+    url='https://github.com/mozilla/telemetry-analysis-service',
+    license='MPL 2.0',
+    classifiers=[
+        'Development Status :: 5 - Production/Stable',
+        'Environment :: Web Environment :: Mozilla',
+        'Framework :: Django',
+        'Intended Audience :: Developers',
+        'License :: OSI Approved :: Mozilla Public License 2.0 (MPL 2.0)',
+        'Programming Language :: Python',
+        'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3.6',
+        'Topic :: Internet :: WWW/HTTP',
+        'Topic :: Scientific/Engineering :: Information Analysis'
+    ],
+    zip_safe=False,
+)