Add missing long_description_content_type to setup.py

Author: Photonios

setup.py

@@ -42,6 +42,7 @@ def run(self):
     license="MIT License",
     description="Bringing all of PostgreSQL's awesomeness to Django.",
     long_description=README,
+    long_description_content_type='text/x-rst',
     url="https://github.com/SectorLabs/django-postgres-extra",
     author="Sector Labs",
     author_email="[email protected]",