Update README.md

Author: kivikakk

README.md

@@ -3,8 +3,8 @@ GitHub Markup
 
 This library is the first step of a journey that every markup file in a repository goes on before it is rendered on GitHub.com:
 
-1. This library converts the raw markup to HTML. See the list of [supported markup formats](#markups) below.
-1. The HTML is sanitized, aggressively removing things that could harm you and your kin—such as `script` tags, inline-styles, and `class` or `id` attributes. See the [sanitization filter](https://github.com/jch/html-pipeline/blob/master/lib/html/pipeline/sanitization_filter.rb) for the full whitelist.
+1. This library selects an _underlying library_ to convert the raw markup to HTML. See the list of [supported markup formats](#markups) below.
+1. The HTML is sanitized, aggressively removing things that could harm you and your kin—such as `script` tags, inline-styles, and `class` or `id` attributes.
 1. Syntax highlighting is performed on code blocks. See [github/linguist](https://github.com/github/linguist#syntax-highlighting) for more information about syntax highlighting.
 1. The HTML is passed through other filters in the [html-pipeline](https://github.com/jch/html-pipeline) that add special sauce, such as [emoji](https://github.com/jch/html-pipeline/blob/master/lib/html/pipeline/emoji_filter.rb), [task lists](https://github.com/github/task_list/blob/master/lib/task_list/filter.rb), [named anchors](https://github.com/jch/html-pipeline/blob/master/lib/html/pipeline/toc_filter.rb), [CDN caching for images](https://github.com/jch/html-pipeline/blob/master/lib/html/pipeline/camo_filter.rb), and  [autolinking](https://github.com/jch/html-pipeline/blob/master/lib/html/pipeline/autolink_filter.rb).
 1. The resulting HTML is rendered on GitHub.com.