deprecation readme

README → README.md

@@ -1,3 +1,25 @@
+# YOMM11 IS DEPRECATED
+
+Thank you for the stars and the feedback!
+
+In 2017 I learned the D language, and I
+implemented
+[an open method library for D](https://github.com/jll63/openmethods.d).  In the
+process I had a few fresh ideas, some of which are applicable to C++. Also, my
+colleague David Goffredo educated me on the power of modern preprocessor
+macros.
+
+Consequently, I set out to re-implement Yomm11 from scratch. The result
+is [Yomm2](https://github.com/jll63/yomm2), which I feel is a much better
+library. Read about the
+improvements
+[here](https://github.com/jll63/yomm2/blob/master/yomm11-yomm2.md).
+
+I will no longer actively develop Yomm11 but I will consider PRs. I strongly
+recommend switching to Yomm2 though.
+
+## Old content:
+
 This library implements open multi-methods for C++11.
 
 Salient features are: