Help with stylesheetparser

I've gone and downloaded the plugin, and put the folder in the plugins folder.

I then put the following code in config.js

config.extraPlugins = 'stylesheetparser';
config.stylesSet = [];
config.contentsCss = 'custom-styles.css';

In the custom-styles.css file I have just one rule:
div.yellow
{
    background:#FFFF00;
    color:#000;
}

The styles dropdown appears blank.  Am I missing something?