Check out https://github.com/kogitant/sonar-slack-notifier-plugin for sonarqube 5.5+
SonarQube plugin for sending notifications to Slack
This plugin sends notifications to a given slack channel. You can configure a webhook, slack user and slack channel as a global or project specific setting.
To build the plugin call mvn clean package (or download the current release). The artifact must be copied to the SONAR_HOME/extensions/plugins folder and sonarqube must be restarted.
Tested for sonarqube 5.2 and 5.3