Zoltan2/Sphynx: Support for edge weights

[egboman]

Sphynx currently supports vertex weights but not edge weights. The natural way to support edge weights, is to create a weighted Laplacian where the off-diagonal entries correspond to the edge weights. The diagonal entries will need to be adjusted to maintain the Laplacian property (all row/column sums are zero). This modification should be done for both the combinatorial and normalized Laplacian.