Thanks for the PR!
LGTM at a first read.
Looks like the remaining travis failure is unrelated to your PR and you can ignore it.

For reference, here is the definition of getmembers:

https://github.com/python/cpython/blob/9dbf5d3bc2033940cdca35440cf08814544f81e4/Lib/inspect.py#L316-358.

It's gotten more complicated than it used to be in order to handle some edge cases.

Thanks for the contribution!

In addition to fixing #142, it also prevents properties from being evaluated unnecessarily. This prevents unintended side-effects (if evaluating a property has a side-effect) and fixes the case where evaluating a property would have raised an error.