make dist: add CONTRIBUTING.md
diff --git a/Makefile.am b/Makefile.am
index 9ba6e8e..d0c813b 100755
--- a/Makefile.am
+++ b/Makefile.am
@@ -86,6 +86,7 @@
 	bower.json \
 	composer.json \
 	contrib \
+	CONTRIBUTING.md \
 	debian \
 	doc \
 	doap.rdf \