website: Updated website README.md push command

We now push changes to the "stable" branch.
diff --git a/README.md b/README.md
index 63ac562..86d1b17 100755
--- a/README.md
+++ b/README.md
@@ -64,7 +64,7 @@
 committed to a local repository they may be submitted for review by executing:
 
 ```
-git push origin HEAD:refs/for/master
+git push origin HEAD:refs/for/stable
 ```
 
 At this stage you may receive an error if you're not registered to contribute