[release] Release geldata 0.4.0. (#59)

Author: dnwpark

README.md

@@ -9,7 +9,7 @@
   <a href="https://github.com/geldata/gel/blob/master/LICENSE">
     <img src="https://img.shields.io/badge/license-Apache%202.0-blue" />
   </a>
-  <a href="https://discord.gg/edgedb">
+  <a href="https://discord.gg/umUueND6ag">
     <img src="https://discord.com/api/guilds/841451783728529451/widget.png" alt="Discord">
   </a>
 </div>

build.gradle

@@ -5,7 +5,7 @@ plugins {
 }
 
 ext {
-    project_version = '0.4.0-SNAPSHOT'
+    project_version = '0.4.0'
     github_org = 'geldata'
     project_name = 'gel-java'
     artifact_group = 'com.geldata'