Change content for SpringBoot 2.0.0.RELEASE (#11)

Author: heowc

prereq_editor_jdk_buildtools.adoc

@@ -1,11 +1,11 @@
 :linkattrs:
 
-ifndef::java_version[:java_version: 1.6]
+ifndef::java_version[:java_version: 1.8]
 
 * About 15 minutes
 * A favorite text editor or IDE
 * http://www.oracle.com/technetwork/java/javase/downloads/index.html[JDK {java_version}] or later
-* http://www.gradle.org/downloads[Gradle 2.3+] or http://maven.apache.org/download.cgi[Maven 3.0+]
+* http://www.gradle.org/downloads[Gradle 4+] or http://maven.apache.org/download.cgi[Maven 3.2+]
 * You can also import the code straight into your IDE:
 ** link:/guides/gs/sts[Spring Tool Suite (STS)]
 ** link:/guides/gs/intellij-idea/[IntelliJ IDEA]

prereq_editor_jdk_maven_buildtools.adoc

@@ -1,9 +1,9 @@
 :linkattrs:
 
-ifndef::java_version[:java_version: 1.6]
+ifndef::java_version[:java_version: 1.8]
 
  - About 15 minutes
  - A favorite text editor or IDE
  - http://www.oracle.com/technetwork/java/javase/downloads/index.html[JDK {java_version}] or later
- - http://maven.apache.org/download.cgi[Maven 3.0+]
+ - http://maven.apache.org/download.cgi[Maven 3.2+]
  - You can also import the code from this guide as well as view the web page directly into link:/guides/gs/sts[Spring Tool Suite (STS)] and work your way through it from there.