disco-0.1.0.0: test/graphs-equality/input

emptyGraph == emptyGraph
vertex(1) + vertex(2) == vertex(2) + vertex(1)
vertex(1) * (vertex 2 + vertex 3) == vertex 1 * vertex 2 + vertex 1 * vertex 3
vertex 1 * vertex 2 * vertex 3 == vertex 1 * vertex 2 + vertex 1 * vertex 3 + vertex 2 * vertex 3