make java package version be based on git tags

Author: asafc

build.gradle

@@ -10,9 +10,10 @@ plugins {
     // Apply the java-library plugin for API and implementation separation.
     id 'java-library'
     id 'maven-publish'
+    id 'com.palantir.git-version' version '0.13.0'
 }
 
-version = "0.0.1"
+version gitVersion()
 
 repositories {
     // Use Maven Central for resolving dependencies.