update server metrics

changes include -
1) metamx/server-metrics#8 - Add custom
dimensions for Jvm and Sys monitors
2) metamx/server-metrics#9 - Add net, tcp,
uptime and cpu metrics

pom.xml

@@ -137,7 +137,7 @@
             <dependency>
                 <groupId>com.metamx</groupId>
                 <artifactId>server-metrics</artifactId>
-                <version>0.2.0</version>
+                <version>0.2.2</version>
             </dependency>
             <dependency>
                 <groupId>commons-codec</groupId>