Update information about contributing

The contents of the HACKING file were hopelessly outdated. Remove the
file and start with a CONTRIBUTING document.
diff --git a/README.cvs-commits b/README.cvs-commits
index a4bd841..9c7bdd0 100644
--- a/README.cvs-commits
+++ b/README.cvs-commits
@@ -1,4 +1,4 @@
- Please read the HACKING file for instructions
+ Please read the CONTRIBUTING file for instructions
 
 Daniel