Generate excerpt content in Jekyll for use on Gihub pages. This extracts the post content within the '<!-- excerpt start -->' and '<!-- excerpt end -->' comment tags.

2012-03-03-demo.md

layout	title
post	Jekyll Excerpts

This text becomes the excerpt text displayed on the main page

This test is not displayed.

index.html

---
layout: default
title: "Main Page"
---

<h2>Recent Posts</h2>
<div class="posts">
  {% for post in site.posts limit:5 %}
    <div class="post">
      <div class="title"><a href="{{ post.url }}">{{post.title }}</a></div>
      <div class="date">Posted on {{ post.date | date: "%B %d %Y" }}</div>
      <div class="excerpt">{{ post.content | split:'<!-- excerpt end -->' | first | split:'<!-- excerpt start -->' | last }}</div>
      <p><a href="{{post.url}}">Read more »</a></p>
    </div>
    <hr />
  {% endfor %}
</div>