Configure Coveralls

[olleolleolle]

This PR configures Coveralls to report to its website.

Problem:

The earlier Travis builds were all using a 0.7.3, which seemed to work locally, but when they landed on the website, the website showed 0%. (They were also not starting the reporting right, and were missing a configuration file.)

Travis log excerpt

``` [Coveralls] Submitting with config: { "environment": { "pwd": "/home/travis/build/savonrb/wasabi", "rails_root": null, "simplecov_root": "/home/travis/build/savonrb/wasabi", "gem_version": "0.7.2", "travis_job_id": "721789725", "travis_pull_request": "false" }, "git": { "head": { "id": "028cf56c25f1e035da2b6c694a9f7b7789fd956d", "committer_name": "Olle Jonsson", "committer_email": "olle.jonsson@gmail.com", "message": "CI: use Bundler cache" }, "branch": "(HEAD detached at 028cf56)", "remotes": [ { "name": "origin", "url": "https://github.com/savonrb/wasabi.git" } ] }, "service_job_id": "721789725", "service_name": "travis-ci" } [Coveralls] Submitting to https://coveralls.io/api/v1 [Coveralls] Job #525.1 [Coveralls] https://coveralls.io/jobs/66943777 Coverage is at 100.0%. Coverage report sent to Coveralls. ```

What we did

The Coveralls Ruby on Rails documentation at https://docs.coveralls.io/ruby-on-rails explained these steps:

• add a configuration file which was missing
• call the Coveralls.wear! method in the spec helper

Result

[coveralls]

Coverage increased (+98.4%) to 98.387% when pulling c6c9fbeff0f0ce904b54c4b32e9de15918b319c1 on use-coveralls-newer into 028cf56c25f1e035da2b6c694a9f7b7789fd956d on master.