Bump version to 1.18.1

debian/changelog

@@ -1,3 +1,9 @@
+dpkg (1.18.1) UNRELEASED; urgency=low
+
+  *
+
+ -- Guillem Jover <guillem@debian.org>  Mon, 18 May 2015 16:08:17 +0200
+
 dpkg (1.18.0) unstable; urgency=low
 
   [ Guillem Jover ]