Merge pull request #22 from scorphus/feature/phantomas_per_metrics_a

Support Phantomas per metrics
Work with local installation of Phantomas

As defined in "setup" in the Makefile, Phantomas is installed as a
local Node.js module. `npm bin´ outputs the "bin" directory path.
Use check_output instead of Popen

As it is necessary to wait until the Popen call finishes, use
check_update instead which already returns the command output as
string. This makes the code simpler.

While testing, check_output_mock needs to return two different
values depending on the arguments. A side_effect function was
defined (check_output_mock_side_effect) to do just that.

Some variables were renamed to a more significant name.