Add MANIFEST.in to include Readme.md in dist

Change-Id: I9f25c3caafc3e7610807e8ddcb76730b26ddc617
diff --git a/MANIFEST.in b/MANIFEST.in
new file mode 100644
index 0000000..78e5c48
--- /dev/null
+++ b/MANIFEST.in
@@ -0,0 +1 @@
+include Readme.md