Strange count_per_link() results for networks generated using ntw.split_arcs()

[anitagraser]

The counts per link are all over the place when I use a split network. I've created a notebook to illustrate the issue:

https://github.com/anitagraser/spaghetti/blob/af4cc443be47c2e0b678b6b4a0deaf970d026207/notebooks/debug-counts-on-split-arcs.ipynb

[jGaboardi]

Related to #527. Resolve this first before proceeding to that issue.

[jGaboardi]

See the original comment here.

[jGaboardi]

This is being fixed in #535. Once I merge that in I plan to follow up with some extra segmentation examples in the network segmentation notebook.