Expose preferred_syntax configuration in README

This is the most important configuration one can set for sass-rails, yet the only reliable place to find it is [StackOverflow](http://stackoverflow.com/questions/6006360/how-to-make-rails-3-1-use-sass-over-scss-as-the-default).

Author: olivierlacan

README.md

@@ -19,17 +19,19 @@ properties that will be passed to Sass.
 The [list of supported options](http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#options)
 can be found on the Sass Website with the following caveats:
 
-1. `:style` - This option is not supported. This is determined by the Rails environment. It's `:expanded` only on development, otherwise it's `:compressed`.
-2. `:never_update` - This option is not supported. Instead set `config.assets.enabled = false`
-3. `:always_update` - This option is not supported. Sprockets uses a controller to access stylesheets in development mode instead of a full scan for changed files.
-4. `:always_check` - This option is not supported. Sprockets always checks in development.
-5. `:syntax` - This is determined by the file's extensions.
-6. `:filename` - This is determined by the file's name.
-7. `:line` - This is provided by the template handler.
+1. `preferred_syntax` - This option determines the default Sass syntax and file extensions that will be used by Rails generators. Can be `:scss` (default CSS-compatible SCSS syntax) or `:sass` (indented Sass syntax).
+2. `:style` - This option is not supported. This is determined by the Rails environment. It's `:expanded` only on development, otherwise it's `:compressed`.
+3. `:never_update` - This option is not supported. Instead set `config.assets.enabled = false`
+4. `:always_update` - This option is not supported. Sprockets uses a controller to access stylesheets in development mode instead of a full scan for changed files.
+5. `:always_check` - This option is not supported. Sprockets always checks in development.
+6. `:syntax` - This is determined by the file's extensions.
+7. `:filename` - This is determined by the file's name.
+8. `:line` - This is provided by the template handler.
 
 ### Example
 
     MyProject::Application.configure do
+      config.sass.preferred_syntax = :sass
       config.sass.line_comments = false
       config.sass.cache = false
     end