fixed bug related to float inaccuracies

include/constants.h

include/edge.h

include/intersections.h

include/split_triangle.h

src/shapes/edge.cpp

src/union.cpp

src/utilities/intersections.cpp

src/utilities/split_triangle.cpp

tests/union_tests.cpp

tests/unit_tests/intersections_tests.cpp

tests/unit_tests/split_triangle_tests.cpp