fixed incorrect command in documentation - user_guide/saving_charts.rst
@@ -42,7 +42,7 @@ Firefox, which requires the following:
code without opening an actual browser window).
If you use homebrew on OSX, this can be installed with::
- $ brew install chromedriver
+ $ brew cask install chromedriver
$ brew install geckodriver
See the ``chromedriver`` or ``geckodriver`` documentation for details on
