Improve arv-run-pipeline-instance's logging when it encounters an error.

no issue #
Be more explicit that hello-world.py is a script which is expected to fail.

no issue #
Another tweak to tutorial-job-debug.html.textile.liquid

no issue #
Whitespace fix.

refs #3219
Be consistent about the version of ruby that is installed by rvm and
used by the various containers. Be consistent about using rvm-exec and
bundle exec in every command that uses ruby.

Add documentation and warning about --realclean option to build.sh

refs #3219
Merge branch '3219-further-docker-improvements'

refs #3219