Polish guide to reference 2.0.0.RELEASE

README.adoc

@@ -7,7 +7,7 @@ experimental: Try the code inside your browser with -> http://beta.codenvy.com/f
 :toc:
 :project_id: gs-rest-service
 :spring_version: current
-:spring_boot_version: 1.5.10.RELEASE
+:spring_boot_version: 2.0.0.RELEASE
 :icons: font
 :source-highlighter: prettify