Change to latest dependency version, add gradle dependency

SeaweedFS-Java-Client.md

@@ -11,12 +11,17 @@ $cd $GOPATH/src/github.com/seaweedfs/seaweedfs/other/java/client
 $ mvn install
 ```
 
-Maven
+Gradle
+```gradle
+implementation 'com.github.chrislusf:seaweedfs-client:3.13'
 ```
+
+Maven
+```xml
 <dependency>
   <groupId>com.github.chrislusf</groupId>
   <artifactId>seaweedfs-client</artifactId>
-  <version>1.6.4</version>
+  <version>3.13</version>
 </dependency>
 ```
 Or you can download the latest version from MavenCentral