Update version to 0.3.0 in README.md to reflect the latest SDK release.

Author: mbasadi

README.md

@@ -10,7 +10,7 @@ Add the following dependency to your project's `pom.xml`:
 <dependency>
     <groupId>com.notificationapi</groupId>
     <artifactId>notificationapi-java-server-sdk</artifactId>
-    <version>0.1.0</version>
+    <version>0.3.0</version>
 </dependency>
 ```