Add link to JIRA article in docs

doc/user/project/integrations/jira.md

 # GitLab JIRA integration
-GitLab can be configured to interact with JIRA. Configuration happens via
-user name and password. Connecting to a JIRA server via CAS is not possible.
-Each project can be configured to connect to a different JIRA instance, see the
-[configuration](#configuration) section. If you have one JIRA instance you can
-pre-fill the settings page with a default template. To configure the template
-see the [Services Templates][services-templates] document.
-Once the project is connected to JIRA, you can reference and close the issues
-in JIRA directly from GitLab.
+GitLab can be configured to interact with [JIRA], a project management platform.
+Once your GitLab project is connected to JIRA, you can reference and close the
+issues in JIRA directly from GitLab.
+For a use case, check out this article of [How and why to integrate GitLab with
+JIRA](https://www.programmableweb.com/news/how-and-why-to-integrate-gitlab-jira/how-to/2017/04/25).
 ## Configuration
+Each GitLab project can be configured to connect to a different JIRA instance.
+If you have one JIRA instance you can pre-fill the settings page with a default
+template, see the [Services Templates][services-templates] docs.
+
+Configuration happens via user name and password. Connecting to a JIRA server
+via CAS is not possible.
+
 In order to enable the JIRA service in GitLab, you need to first configure the
 project in JIRA and then enter the correct values in GitLab.
@@ -213,3 +217,4 @@ your project needs to close a ticket.
 [services-templates]: services_templates.md
 [jira-repo-old-docs]: https://gitlab.com/gitlab-org/gitlab-ce/blob/8-13-stable/doc/project_services/jira.md
+[jira]: https://www.atlassian.com/software/jira