Fix CI configuration.

...to actually run tests.

Ow.

(You can tell I don't really look to travis for meaningful results.)

I am embarrassed to say I ripped out the *actual* running of tests
back during 804a1336, when cleaning
up codecov tools.

Thanks to @mvdan for looking at the CI and CI config!

.travis.yml

@@ -16,4 +16,4 @@ install:
 before_script:
 - go fmt ./...
 - go build ./...
-- go test -run xxxx ./...
+- go test ./...