Keep numpy version below 1.16.0

[csala]

The latest version of numpy, 1.16.0, released 2 days ago, is incompatible with the current scikit-image version: scikit-image/scikit-image#3649

numpy should be kept back below 0.16.0 at least until a new scikit-image patch is released and we upgrade our dependencies to include it.

[stefanv]

skimage v0.14.2 has been released to address the issue.

[csala]

Great! Thanks for the heads up @stefanv!
We will upgrade to the new version asap.