Fix background color for code snippets in docs

* Change Copyright in docs for current year

Author: artembilan

build.gradle

@@ -922,17 +922,16 @@ asciidoctor {
 		}
 	}
 	options doctype: 'book', eruby: 'erubis'
+
 	attributes 'docinfo': 'shared',
-		// use provided stylesheet
 		stylesdir: "css/",
 		stylesheet: 'spring.css',
 		'linkcss': true,
 		'icons': 'font',
 		'sectanchors': '',
-		// use provided highlighter
 		'source-highlighter=highlight.js',
 		'highlightjsdir=js/highlight',
-		'highlightjs-theme=atom-one-dark-reasonable',
+		'highlightjs-theme': 'github',
 		'idprefix': '',
 		'idseparator': '-',
 		'spring-version': project.version,

src/reference/asciidoc/index-header.adoc

@@ -6,7 +6,7 @@ ifdef::backend-html5[]
 *{project-version}*
 endif::[]
 
-(C) 2009 - 2019 Pivotal Software, Inc.
+(C) 2009 - 2020 Pivotal Software, Inc.
 All rights reserved.
 
 Copies of this document may be made for your own use and for distribution to others, provided that you do not charge any fee for such copies and further provided that each copy contains this Copyright Notice, whether distributed in print or electronically.