add duo-test

@ianstormtaylor i removed phantomjs args for now, tests pass, do we need those args ?
anyways, `duo-test(1)` will support passing the args via `-- --phantom-arg --another-arg value` etc..

cc @lancejpollard @ianstormtaylor 
i'm -1 on these kinds of variables. just since its used twice doesnt mean we need to variable it, since it makes it way harder to read