Add a check for the symbols used in ColoringProblem and ConstantColoringAlgorithm

[amontoison]

I didn't know that the order of the symbols were different for ColoringProblem and ConstantColoringAlgorithm.
I was able to create problem and algo but it took me a few minutes why the dispatch was not working for compress.

problem = ColoringProblem{:nonsymmetric,:column}()
algo = ConstantColoringAlgorithm{:column,:nonsymmetric}(B, color)
result = coloring(B, problem, algo)
C = compress(B, result)

[gdalle]

That's because initially there was no ConstantColoringAlgorithm for symmetric matrices, and so when I added that option I added the symbol as a last time parameter to make it non breaking. Good idea to check more thoroughly