[maven-release-plugin] prepare release narya-1.18

pom.xml

@@ -5,7 +5,7 @@
   <groupId>com.threerings</groupId>
   <artifactId>narya-parent</artifactId>
   <packaging>pom</packaging>
-  <version>1.18-SNAPSHOT</version>
+  <version>1.18</version>
 
   <name>Narya Parent</name>
   <description>Facilities for making networked multiplayer games.</description>
@@ -34,7 +34,7 @@
     <connection>scm:git:git://github.com/threerings/narya.git</connection>
     <developerConnection>scm:git:git@github.com:threerings/narya.git</developerConnection>
     <url>https://github.com/threerings/narya/</url>
-    <tag>HEAD</tag>
+    <tag>narya-1.18</tag>
   </scm>
 
   <modules>