Convert README to .rst for PyPI.
diff --git a/MANIFEST.in b/MANIFEST.in
index 0c28801..5bec85d 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,5 +1,5 @@
 recursive-include WiringPi *.h
-include README.md
+include README.rst
 include LICENSE.txt
 include bindings.i
 include constants.py