better header/footer template, add syntax highlighting

templates/tag.html

@@ -1,3 +1,6 @@
+{% extends "base.html" %}
+
+{% block content %}
 branch: {{tag.ref_name}}<br/>
 hash: {{tag.full_hash}} ({{tag.short_hash}})<br/>
 author: {{tag.author.name}}<br/>
@@ -9,3 +12,4 @@ summary: {{tag.summary}}<br/>
 commit: {%- if commit -%}<a href="../commit/{{commit.full_hash}}.html">{{commit.full_hash}}</a>
 <pre>{{commit.message}}</pre>
 {%-else-%}{{tag.tagged_id}}{%-endif-%}<br/>
+{% endblock content %}