Add content type for long description

Author: uvchik

setup.py

@@ -18,6 +18,7 @@ def read(fname):
           'windpowerlib': [os.path.join('data', '*.csv'),
                            os.path.join('oedb', '*.csv')]},
       long_description=read('README.rst'),
+      long_description_content_type='text/x-rst',
       zip_safe=False,
       install_requires=['pandas >= 0.19.1, < 0.25',
                         'requests < 3.0'],