Disable some tests for mac

Created by: Zaharid

Running tests on mac is expensive, and it involves a lot of false positives on Travis due to various poorly understood timeouts. Considering that we run most of the production on linux and we expect most higher level stuff (such as plots) to be similar enough, it is probably reasonable to disable some tests on Mac, given the current constraints.

We could start disabling the plot tests, which may be causing #676 (closed). That should be doable with pytest. See e.g.

https://docs.pytest.org/en/latest/example/markers.html#marking-platform-specific-tests-with-pytest

For example we could redefine the plot decorator to also skip darwin.