[maven-release-plugin] prepare release v1.6.0

Author: jodastephen

pom.xml

@@ -10,7 +10,7 @@
   <artifactId>threeten-extra</artifactId>
   <packaging>jar</packaging>
   <name>ThreeTen-Extra</name>
-  <version>1.6.0-SNAPSHOT</version>
+  <version>1.6.0</version>
   <description>Additional functionality that enhances JSR-310 dates and times in Java SE 8 and later</description>
   <url>https://www.threeten.org/threeten-extra</url>
 
@@ -144,7 +144,7 @@
     <connection>scm:git:https://github.com/ThreeTen/threeten-extra.git</connection>
     <developerConnection>scm:git:https://github.com/ThreeTen/threeten-extra.git</developerConnection>
     <url>https://github.com/ThreeTen/threeten-extra</url>
-    <tag>HEAD</tag>
+    <tag>v1.6.0</tag>
   </scm>
   <organization>
     <name>ThreeTen.org</name>