Adds setup option --only-links
Makes 'submit' return the job identifier

This is both for the API (RemoteQueue#submit()) and the CLI
('tej submit').
Fixes printing status's arg on PY3
Functional tests
Pulls my fork of scp.py on Travis

Waiting for https://github.com/jbardin/scp.py/pull/39
Merge branch 'master' into 'vistrails'