Make 'cargo test' work

[SimonSapin]

At least some of the reason is that 9f78ea9 did not update test expectations.

Once this is fixed, cargo test should be added to .travis.yml.

[emilio]

cargo test is not expected to work, nor be up to date. It was a churn to add new tests and modify expectations, so I added the make test command.

Agreed that should be better to use a rust harness though.

[SimonSapin]

Then maybe remove the tests that are not expected to pass? They’ll be in the git history when it’s time to bring them back.

[fitzgen]

I think we need a better story than we currently have for running tests, if only for potential contributors and newcomers to this code base.

Right now, I run make test and get no message about whether the test suite overall passed or had failures. I can't even rely on $?. If I look into .travis.yml, I'll find that finding out if my test run passed effectively relies on git diff'ing the test/expectations directory. But I can't even do make test on master without getting diffs in that directory!

This is not friendly for contributors. We need a much better story here.