Upgrade to Gradle 3.4

Closes gh-283

build.gradle

@@ -5,11 +5,15 @@ buildscript {
 		maven { url 'https://plugins.gradle.org/m2/' }
 	}
 	dependencies {
-		classpath 'io.spring.gradle:dependency-management-plugin:0.5.5.RELEASE'
 		classpath 'org.springframework.build.gradle:propdeps-plugin:0.0.7'
-		classpath 'io.spring.gradle:spring-io-plugin:0.0.5.RELEASE'
+		classpath 'io.spring.gradle:spring-io-plugin:0.0.6.RELEASE'
 		classpath 'org.sonarsource.scanner.gradle:sonarqube-gradle-plugin:1.2'
 	}
+	configurations.classpath.resolutionStrategy.eachDependency {
+		if (it.requested.name == 'dependency-management-plugin') {
+			it.useVersion '1.0.0.RELEASE'
+		}
+	}
 }
 
 allprojects {

buildSrc/src/main/groovy/org/springframework/restdocs/build/SampleBuildConfigurer.groovy

@@ -121,7 +121,7 @@ public class SampleBuildConfigurer {
 	private Task createVerifyIncludes(Project project, File buildDir) {
 		Task verifyIncludesTask = project.tasks.create("${name}VerifyIncludes")
 		verifyIncludesTask.description = "Verifies the includes in the ${name} sample"
-		verifyIncludesTask << {
+		verifyIncludesTask.doLast {
 			Map unprocessedIncludes = [:]
 			buildDir.eachFileRecurse { file ->
 				if (file.name.endsWith('.html')) {

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Mon Apr 04 11:55:32 BST 2016
+#Fri Mar 03 15:03:17 GMT 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.12-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-3.4-bin.zip