Start refactoring tests

ci/travis/test.sh

src/sakia/app.py

src/sakia/money/quantitative.py

src/sakia/tests/conftest.py

src/sakia/tests/unit/core/graph/__init__.py

src/sakia/tests/unit/core/graph/test_base_graph.py

src/sakia/tests/unit/core/graph/test_explorer_graph.py

src/sakia/tests/unit/core/graph/test_wot_graph.py

src/sakia/tests/unit/core/money/test_quantitative.py