Update the theme README.md

The `grunt css-themes` command now loops through all Sass files. There is no need to add the newly created file to the task list.

css/theme/README.md

@@ -4,7 +4,7 @@ Themes are written using Sass to keep things modular and reduce the need for rep
 
 ## Creating a Theme
 
-To create your own theme, start by duplicating any ```.scss``` file in [/css/theme/source](https://github.com/hakimel/reveal.js/blob/master/css/theme/source) and adding it to the compilation list in the [Gruntfile](https://github.com/hakimel/reveal.js/blob/master/Gruntfile.js).
+To create your own theme, start by duplicating a ```.scss``` file in [/css/theme/source](https://github.com/hakimel/reveal.js/blob/master/css/theme/source). It will be automatically compiled by Grunt from Sass to CSS (see the [Gruntfile](https://github.com/hakimel/reveal.js/blob/master/Gruntfile.js)) when you run `grunt css-themes`.
 
 Each theme file does four things in the following order:
 
@@ -19,5 +19,3 @@ This is where you override the default theme. Either by specifying variables (se
 
 4. **Include [/css/theme/template/theme.scss](https://github.com/hakimel/reveal.js/blob/master/css/theme/template/theme.scss)**
 The template theme file which will generate final CSS output based on the currently defined variables.
-
-When you are done, run `grunt css-themes` to compile the Sass file to CSS and you are ready to use your new theme.