added unique filtering and config limit param

I hacked some code from other modules and some quick googling, first time with py so this may need to be cleaned up.

The functionality is to have a config var in pythonconfig.py and to remove the duplicates `sorted(set())`

pelican/plugins/related_posts.py

@@ -13,14 +13,21 @@ To enable, add
     from pelican.plugins import related_posts
     PLUGINS = [related_posts]
 
-to your settings's file pelicanconf.py .
+to your pelicanconf.py.
+
+Control the number of entries with in the config file with:
+
+RELATED_POSTS = {
+   'numentries': 6,
+}
+
 
 Usage
 -----
     {% if article.related_posts %}
         <ul>
         {% for related_post in article.related_posts %}
-            <li>{{ related_post }}</li>
+            <li><a href="{{ related_post.url }}">{{ related_post.title }}</a></li>
         {% endfor %}
         </ul>
     {% endif %}
@@ -40,12 +47,24 @@ def add_related_posts(generator, metadata):
 
         if len(related_posts) < 1:
             return
+        
+        metadata["related_posts"] = sorted(set(related_posts))
 
         relation_score = dict(list(zip(set(related_posts), list(map(related_posts.count,
                               set(related_posts))))))
         ranked_related = sorted(relation_score, key=relation_score.get)
+        
+        #Load the confg file and get the number of entries specified there
+        settings =  generator.settings
+        config = settings.get('RELATED_POSTS', {})
 
-        metadata["related_posts"] = ranked_related[:5]
+        #check if the related_posts var is set in the pythonconfig.py
+        if not isinstance(config, dict):
+            info("realted_links plugin: Using default number of related links ("+numentries+")")
+        else:
+            numentries = config.get('numentries', 5)
+        
+        metadata["related_posts"] = ranked_related[:numentries]
 
 
 def register():