dependency cleanup

- install matplotlib instead of matplotlib-base for Python 2.7 (also works in 3)
- used same version pins in setup.py and test_env.yaml
- removed numpy from testing dep in setup.py as it is a package dep

ci/conda-envs/test_env.yaml

@@ -5,8 +5,7 @@ channels:
 dependencies:
 - python
 - six
-- numpy
-- scipy
-- matplotlib-base
-- pandas
+- numpy>=1.0
+- matplotlib
+- pandas>=0.17
 - numkit

setup.py

@@ -66,6 +66,6 @@
                         'numkit',       # numerical helpers
                         'matplotlib',
                         ],
-      tests_require=['pytest', 'numpy>=1.0', 'pandas>=0.17'],
+      tests_require=['pytest', 'pandas>=0.17'],
       zip_safe=True,
       )