Switch README to ReStructuredText format so PyPI is happy

Change-Id: I40f1ef32a4a2b8e816e53867f37a255fa2244bf4
diff --git a/setup.py b/setup.py
index 4b60c7e..a1a6056 100644
--- a/setup.py
+++ b/setup.py
@@ -29,7 +29,7 @@
 version_file = path.join(setup_dir, "VERSION")
 
 # Get the long description from the README file
-with open(path.join(setup_dir, 'README.md'), encoding='utf-8') as f:
+with open(path.join(setup_dir, 'README.rst'), encoding='utf-8') as f:
     long_description = f.read()
 
 with open(version_file) as version_file: