Make the repo deprecation notice more visible

People keep submitting changes to this repo even though it has been deprecated.

Author: mitio

README.md

@@ -1,6 +1,3 @@
-# CodeEUCertificates
-
-Instructions:
-$ python pyploma.py "Name Surname" Event_ID
+# This repo is DEPRECATED.
 
 **Note**: The logic from this repo has been integrated into <https://github.com/codeeu/coding-events> and this repo is now obsolete.