Expose code-coverage

Send coverage information from [travis build](https://travis-ci.org/toopay/framework/jobs/9571715) to [expose code-coverage](https://coveralls.io/builds/132633) [![Coverage Status](https://coveralls.io/repos/toopay/framework/badge.png?branch=master)](https://coveralls.io/r/toopay/framework?branch=master) (require the repo owner to enable this repo in [coveralls](https://coveralls.io/)). This will help committers to see the blindspot within codebase.