Ternary contour plot (#1413)

Prototype of Ternary contour figure factory

Author: emmanuelle

Diff for: plotly/figure_factory/README.md

@@ -142,6 +142,10 @@ It is often not a good idea to put all your code into your `create_foo()` functi
 
 It is best to make all other functions besides `create_foo()` secret so a user cannot access them. This is done by placing a `_` before the name of the function, so `_aux_func()` for example.
 
+6. Tests
+
+Add unit tests in 
+`plotly/tests/test_optional/test_figure_factory/test_figure_factory.py`.
 
 ## Create a Pull Request
 

Diff for: plotly/figure_factory/__init__.py

@@ -18,6 +18,7 @@
 from plotly.figure_factory._scatterplot import create_scatterplotmatrix
 from plotly.figure_factory._streamline import create_streamline
 from plotly.figure_factory._table import create_table
+from plotly.figure_factory._ternary_contour import create_ternary_contour
 from plotly.figure_factory._trisurf import create_trisurf
 from plotly.figure_factory._violin import create_violin
 if optional_imports.get_module('pandas') is not None: