update version for v2.2.0 release

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>org.apache.spark.ml</groupId>
     <artifactId>spark-iforest</artifactId>
-    <version>1.0-SNAPSHOT</version>
+    <version>2.2.0</version>
 
     <properties>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
@@ -133,4 +133,4 @@
     </build>
 
 
-</project>
\ No newline at end of file
+</project>