Updated method for ternary plot (#1418)

New implementation of the ternary contour figure factory that renders contours using filled line traces on top of the the proper ternary contour axes.

Author: emmanuelle

Diff for: .circleci/create_conda_optional_env.sh

@@ -16,7 +16,7 @@ if [ ! -d $HOME/miniconda/envs/circle_optional ]; then
     # Create environment
     # PYTHON_VERSION=3.6
     $HOME/miniconda/bin/conda create -n circle_optional --yes python=$PYTHON_VERSION \
-requests six pytz retrying psutil pandas decorator pytest mock nose poppler xarray
+requests six pytz retrying psutil pandas decorator pytest mock nose poppler xarray scikit-image
 
     # Install orca into environment
     $HOME/miniconda/bin/conda install --yes -n circle_optional -c plotly plotly-orca