add redmine.org issue link of jruby IO.popen() at .travis.yml (#19091)

git-svn-id: http://svn.redmine.org/redmine/trunk@14012 e93f8b46-1217-0410-a6f0-8f06a7374b81

Author: marutosi

.travis.yml

@@ -11,6 +11,7 @@ rvm:
 matrix:
   allow_failures:
     # SCM tests fail randomly due to IO.popen().
+    # http://www.redmine.org/issues/19091
     # https://github.com/jruby/jruby/issues/779
     - rvm: jruby
 env: