Fix markdown rendering on Python Package Index

setup.py

@@ -5,10 +5,12 @@ with open('README.md', 'r') as f:
 
 setup(
     name='scaling',
-    version='0.2.1',
+    version='0.2.3',
     packages=['scaling'],
     install_requires=['pint'],
     author='Dan Howe',
     author_email='d.howe@wrl.unsw.edu.au',
     url='https://github.com/onewhaleid/scaling',
-    description='convert units using Froude and Reynolds similitude')
+    description='convert units using Froude and Reynolds similitude',
+    long_description=long_description,
+    long_description_content_type='text/markdown')