Update maintenance badge

Signed-off-by: Sebastian Hoß <mail@shoss.de>

README.asciidoc

@@ -17,7 +17,7 @@ image:https://img.shields.io/coveralls/{github-org}/{project-name}/master.svg?st
 image:https://img.shields.io/coverity/scan/{coverity-project}.svg?style=flat-square["Coverity Scan Result", link="https://scan.coverity.com/projects/{github-org}-{project-name}"]
 image:https://img.shields.io/codacy/grade/{codacy-project}.svg?style=flat-square["Codacy Code Quality", link="https://www.codacy.com/app/mail_7/{project-name}"]
 image:https://img.shields.io/badge/forkable-yes-brightgreen.svg?style=flat-square["Can this project be forked?", link="https://basicallydan.github.io/forkability/?u={github-org}&r={project-name}"]
-image:https://img.shields.io/maintenance/yes/2016.svg?style=flat-square["Is this thing still maintained?"]
+image:https://img.shields.io/maintenance/yes/2017.svg?style=flat-square["Is this thing still maintained?"]
 image:https://img.shields.io/bountysource/team/metio/activity.svg?style=flat-square["Bounties on open tickets", link="https://www.bountysource.com/teams/metio"]
 
 Utility library for null analysis in Java projects.