Merge pull request #3 from nrudenko/master

Possibility use links of attached files in markup.  Thanks @nrudenko!
Updated labeling to expand tokens
(cherry picked from commit bcba826c1207621de57d58555913ef093ba2aa8b)

Signed-off-by: Joe Hansche <jhansche@meetme.com>
[FIXED JENKINS-21624] Misconfiguration leads to error.

If the "Attached archived artifacts" option is selected, but no
artifacts are configured to be archived by the job, the upload
fails with a `NullPointerException`.

Instead, we should detect that case and log a message indicating
that nothing is going to be uploaded.