Strip tags from title when within tag attribute

The change mentioned in getpelican#336 stripped tags properly in some places but
seems to have forgotten at least one location in the main index.html

pelican/themes/notmyidea/templates/index.html

@@ -29,7 +29,8 @@ <h1>Other articles</h1>
             {% endif %}
             <li><article class="hentry">    
                 <header>
-                        <h1><a href="{{ SITEURL }}/{{ article.url }}" rel="bookmark" title="Permalink to {{ article.title}}">{{ article.title }}</a></h1>
+                    <h1><a href="{{ SITEURL }}/{{ article.url }}" rel="bookmark"
+                           title="Permalink to {{ article.title|striptags }}">{{ article.title }}</a></h1>
                 </header>
 
                 <div class="entry-content">