return types changed in watershed

[k-dominik]

https://github.com/constantinpape/elf/blob/9979a9dee7b34ab7ca161817f6f25cb592ffd8a0/elf/segmentation/watershed.py#L164

Heya, just curious as to why the return type here has changed. I think vigra (which is used internally) will always return uint32 and that way it was easy to "remain" in the vigra regime. Now one has to cast again. Are you working on replacing vigra for the watershed?

Cheers D