Add content type of long description

Author: uvchik

setup.py

@@ -17,6 +17,7 @@ def read(fname):
       package_data={
           'windpowerlib': [os.path.join('data', '*.csv')]},
       long_description=read('README.rst'),
+      long_description_content_type='text/rst',
       zip_safe=False,
       install_requires=['pandas >= 0.19.1, < 0.26',
                         'requests < 3.0'],