Add cython to Circle CI

Author: rth

.circleci/config.yml

@@ -14,7 +14,7 @@ jobs:
             conda update --yes --quiet conda
             conda create -n testenv --yes --quiet python=3
             source activate testenv
-            conda install --yes pip numpy scipy scikit-learn matplotlib sphinx sphinx_rtd_theme numpydoc pillow
+            conda install --yes pip numpy scipy scikit-learn matplotlib sphinx sphinx_rtd_theme numpydoc pillow cython nomkl
             pip install sphinx-gallery
             pip install .
             cd doc