Add nohttp check to build. Upgrade gradle and asciidoctor plugin.

build.gradle

@@ -11,7 +11,8 @@ buildscript {
 	dependencies {
 		classpath 'io.spring.gradle:propdeps-plugin:0.0.10.RELEASE'
 		classpath 'io.spring.gradle:spring-io-plugin:0.0.8.RELEASE'
-		classpath 'org.asciidoctor:asciidoctor-gradle-plugin:1.5.3'
+		classpath 'org.asciidoctor:asciidoctor-gradle-plugin:1.5.12'
+		classpath 'io.spring.nohttp:nohttp-gradle:0.0.1.RELEASE'
 	}
 }
 
@@ -28,6 +29,12 @@ ext {
 	] as String[]
 }
 
+apply plugin: 'io.spring.nohttp'
+
+checkstyle {
+	toolVersion = 8.16
+}
+
 subprojects {
 	apply plugin: 'java'
 	apply plugin: 'maven'
@@ -100,7 +107,6 @@ subprojects {
 
 	repositories {
 		mavenCentral()
-		maven { url "https://repo.spring.io/libs-milestone" }
 	}
 }
 
@@ -167,6 +173,10 @@ configure(rootProject) {
 		archives docsZip
 		archives schemaZip
 	}
+
+	repositories {
+		mavenCentral()
+	}
 }
 
 ext {
@@ -202,7 +212,3 @@ task dist(dependsOn: assemble) {
 	group = 'Distribution'
 	description = 'Builds -dist, -docs and -schema distribution archives.'
 }
-
-task wrapper(type: Wrapper) {
-	gradleVersion = '4.2.1'
-}

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.10-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.2.1-bin.zip