Allow passing args to workers through cluster.setupMaster() through opt.args
Fix syntax error
Add test for passing args to workers
Set args through cluster.settings instead of cluster.setupMaster() so that the test passes

The test failed because cluster.setupMaster() can only be called once and has already been called due to previous tests.
Assigning the args directly to cluster.settings.args seems to do the trick.
Merge pull request #16 from sbergmann/master

Support passing arguments to workers