[TASK] Drop the travis linting from the test rake task.

travis-lint has been discontinued. As we change the travis configuration
very seldomly, we do not need to check it automatically on each run.

Travis will complain about invalid configuration files anyway.

Resolves: GET-4
Merge pull request #45 from braingourmets/task/travis-lint

[TASK] Drop the travis linting from the test rake task.