Add generic descriptions for templates

Fixes #8
diff --git a/templates/author.html b/templates/author.html
index c2decd3..ee17552 100644
--- a/templates/author.html
+++ b/templates/author.html
@@ -1,6 +1,8 @@
 {% extends "index.html" %}
 {% block title %}Author: {{ author }} | {{ SITENAME }}{% endblock %}
 
+{% block description %}Posts by {{ author }} on this site{% endblock %}
+
 {% block subheader %}
 <p>Author: {{ author }}</p>
 {% endblock %}