Updated asciidoctor plugin version. Extracted dropwizard version numb…

…er out to build property

build.gradle

@@ -9,7 +9,7 @@ buildscript {
 }
 
 plugins {
-    id 'org.asciidoctor.convert' version '1.5.3'
+    id 'org.asciidoctor.convert' version '1.5.9.2'
 }
 
 version "2.0.0.RC1"
@@ -18,6 +18,10 @@ group "org.grails.plugins"
 apply plugin:"org.grails.grails-plugin"
 apply plugin:"org.grails.grails-plugin-publish"
 
+ext {
+    dropwizard_version = '4.1.5'
+}
+
 repositories {
     mavenLocal()
     maven { url "https://repo.grails.org/grails/core" }
@@ -42,7 +46,7 @@ dependencies {
     compile "org.grails.plugins:cache"
     compile "org.grails.plugins:scaffolding"
     console "org.grails:grails-console"
-    compile 'io.dropwizard.metrics:metrics-core:4.1.5'
+    compile "io.dropwizard.metrics:metrics-core:${dropwizard_version}"
     profile "org.grails.profiles:web-plugin"
     testCompile "org.grails:grails-testing-support"
     testCompile "org.grails:grails-web-testing-support"