Update latest staging plugin example to 1.6.6 and provide link to dow…

…nload latest plugin

chapter-staging.asciidoc

@@ -432,7 +432,7 @@ by adding it to the project build plugins section as an extension:
     <plugin>
       <groupId>org.sonatype.plugins</groupId>
       <artifactId>nexus-staging-maven-plugin</artifactId>
-      <version>1.6.3</version>
+      <version>1.6.6</version>
       <extensions>true</extensions>
       <configuration>
         <serverId>nexus</serverId>
@@ -444,7 +444,7 @@ by adding it to the project build plugins section as an extension:
 NOTE: It is important to use a version of the plugin that is compatible with your {pro} server. Version 1.2 is
 compatible with {pro} 2.3, Version 1.4.4 is compatible with {pro} 2.4, Version 1.4.8 is compatible with {pro} 2.5
 and 2.6. 1.5 and 1.6.x can be used for {pro} 2.7 to 2.10. The latest version of the plugin available is always
-compatible with the latest available version of {pro}. Try to use the newest possible plugin version to take
+compatible with the latest available version of {pro}. Try to use the http://search.maven.org/#search%7Cga%7C1%7Ca%3A%22nexus-staging-maven-plugin%22[newest possible plugin] version to take
 advantage of any available improvements.
 
 Following Maven best practices, the version should be pulled out into a