Allow pickles when loading test fixture data.

[QuLogic]

NumPy disabled loading pickles because it was a security risk, but the test fixture data is test data we need to load as pickles.

This is still a security risk though, and just a stopgap solution. See #189.

TODO:

• [-] Unit tests and/or doctests in docstrings
• tox -e py37 passes locally
• tox -e py27 passes locally
• [-] Docstrings and API docs for any new/modified user-facing classes and functions
• [-] Changes documented in docs/release.rst
• [-] tox -e docs passes locally
• AppVeyor and Travis CI passes
• Test coverage to 100% (Coveralls passes)

[jakirkham]

Thanks @QuLogic! 😄