For #194, convert the POTD management command to a celery task. Refactored to put the logic for the command into a function, and the command simply calls this function. The task can also just call this function. Added some basic tests for the new function.

{% extends 'weblinks/base.html' %}
{% block title %}Web Links: {{ link.title }}{% endblock %}
{% block weblinks_content %}
<h3>Link Details: {{ link.title }}</h3>
<dl>
{% include 'weblinks/link.html' %}
</dl>
{% endblock %}