Unstable builds are not displayed correctly

[reuterbal]

In the 'Jenkins'-tab of a project, unstable jobs are not displayed correctly. The following patch fixes this:

--- a/app/use_cases/jenkins_jobs/base.rb
+++ b/app/use_cases/jenkins_jobs/base.rb
@@ -175,6 +175,8 @@ module JenkinsJobs
           'success'
         when 'red'
           'failure'
+        when 'yellow'
+          'unstable'
         when 'notbuilt'
           'notbuilt'
         when 'blue_anime'