Use gradle-versions-plugin to check for dependency updates.

+ This plugin adds the "dependencyUpdates" Gradle task.
+ Configure to only offer stable versions.
+ Plugin website: https://github.com/ben-manes/gradle-versions-plugin

build.gradle

@@ -3,8 +3,11 @@ plugins {
     id "idea"
     id "org.jetbrains.intellij" version "0.4.13"
     id "com.github.johnrengelman.shadow" version "5.1.0"
+    id "com.github.ben-manes.versions" version "0.33.0"
 }
 
+apply from: "gradle/versions.gradle"
+
 sourceCompatibility = javaVersion
 targetCompatibility = javaVersion
 

gradle/versions.gradle

@@ -0,0 +1,14 @@
+// Gradle Versions Plugin
+
+tasks.named("dependencyUpdates").configure {
+    def isNonStable = { String version ->
+        def stableKeyword = ["RELEASE", "FINAL", "GA"].any {
+            qualifier -> version.toUpperCase().contains(qualifier)
+        }
+        def regex = /^[0-9,.v-]+(-r)?$/
+        return !stableKeyword && !(version ==~ regex)
+    }
+    rejectVersionIf {
+        isNonStable(it.candidate.version)
+    }
+}