Release Notes (0.16.1)

The 0.16.1 release fixes several user-discovered bugs, and updates the versons of several dependencies:

* `#207 <https://github.com/AllenInstitute/AllenSDK/issues/207>` Fix two missing ephys features (tau and max_euclidean_distance)
* `#256 <https://github.com/AllenInstitute/AllenSDK/issues/256>`_ Making sure our examples are python3 compatible
* `#267 <https://github.com/AllenInstitute/AllenSDK/issues/267>`_ Fix a bug in get_cell_specimens filter argument
* `#295 <https://github.com/AllenInstitute/AllenSDK/issues/295>`_ BiophysicalApi.get_neuronal_models doesn't find perisomatic models
* `#426 <https://github.com/AllenInstitute/AllenSDK/issues/426>`_ numpy and pytables versions pinned until pytables 3.5 can be pip installed

Additionally, serveral dependencies were upgraded to resolve installation issues:

* numpy==1.15.4
* numpy==3.4.4
* pytest>=4.1.1
* pip install Pillow (Needed in CI infrastrucutre)
* For python 2.7 conda install -c conda-forge scikit-image (Needed in CI infrastructure)

We also removed deprecated functionality in BrainObservatoryNwbDataSet, and wrote some additional tools for working with itksnap label descriptions <https://github.com/AllenInstitute/AllenSDK/issues/312>_.