Tests

Those are just simple tests, mainly created as exampless skel interface and to create simple run cases for all workflows.

While branch is named unit_test, those are more of integration tests, which is fine with me.  They meet "test as documentation" criteria, and they cover existing code in 82%. And as such they should be good determinant of any future changes.

To run test use rebar:

`$./rebar eunit`