Add Sub_parts to plugin list. Fix Markdown.

Readme.rst

@@ -184,6 +184,8 @@ Static comments           Allows you to add static comments to an article
 
 Subcategory               Adds support for subcategories
 
+Sub parts                 Break a very long article in parts, without polluting the timeline with lots of small articles.
+
 Summary                   Allows easy, variable length summaries directly embedded into the body of your articles
 
 tag_cloud                 Provides a tag_cloud

sub_parts/README.md

@@ -56,9 +56,9 @@ For example, add the following to the template `article.html`:
 
 ## Known use cases
 
-<pxquim.pt> uses sub-parts and the plug-in Pictures to publish photo galleries with thousands of photos. Sub-parts break the photo galleries into manageable chunks, possibly with different tags and authors.
+[pxquim.pt](http://pxquim.pt/) uses sub-parts and the plug-in Pictures to publish photo galleries with thousands of photos. Sub-parts break the photo galleries into manageable chunks, possibly with different tags and authors.
 
-<pxquim.com> uses sub-parts to cover conferences, where it makes sense to have a sub-part for each speaker.
+[pxquim.com](http://pxquim.com/) uses sub-parts to cover conferences, where it makes sense to have a sub-part for each speaker.
 
 ## What is the difference between Sub-part and Series?