Sort go tests by name within a package

We're using goconvey for go tests using stretchr/testify/suite. Our suites run in parallel, so the tests from each suite are all mixed up in random order.

This patch stabilizes the output by sorting tests by their name. Combined with https://github.com/stretchr/testify/pull/105, we also get our tests grouped by suite when they're alphabetized.

I didn't add more tests, but the existing tests are re-ordered from the original go test log order anyway.