Upgrade plugins to Kotlin 1.2.71 and Asciidoctor 1.5.9

Author: jhoeller

build.gradle

@@ -11,9 +11,9 @@ buildscript {
 // 3rd party plugin repositories can be configured in settings.gradle
 plugins {
 	id "io.spring.dependency-management" version "1.0.5.RELEASE" apply false
-	id "org.jetbrains.kotlin.jvm" version "1.2.70" apply false
+	id "org.jetbrains.kotlin.jvm" version "1.2.71" apply false
 	id "org.jetbrains.dokka" version "0.9.17"
-	id "org.asciidoctor.convert" version "1.5.7"
+	id "org.asciidoctor.convert" version "1.5.9"
 }
 
 ext {