Fix ca file absolute path.

Allow to use a custom path instead of the default ca file.
Make sure the ca file exist.
Merge pull request #37 from codeclimate/fix_ca_file_path

Fix ca file absolute path.
Merge branch 'master' into travis_conf

* master:
  Make sure the ca file exist.
  Fix ca file absolute path.
Report test coverage.

And Notify slack about builds.