Fixing broken pypi long description rendering (appium#303)

pr4bh4sh · KazuCocoa · commit 0330728611af · 2018-12-22T11:58:16.000+09:00
reference: https://packaging.python.org/guides/making-a-pypi-friendly-readme Tested at https://pypi.org/project/delayed-assert
diff --git a/setup.py b/setup.py
@@ -23,6 +23,7 @@
     version=library_version(),
     description='Python client for Appium',
     long_description=io.open(os.path.join(os.path.dirname('__file__'), 'README.md'), encoding='utf-8').read(),
+    long_description_content_type='text/markdown',
     keywords=[
         'appium',
         'selenium',
