Replace fixed urls with their names.

[procrasti]

After you've completed the first tutorial, you will see you can name urls, and we shouldn't link to them with hardcoded urls, but by their name.

So, in common_links and the other fragments, replace the hardcoded urls with:

For example,

{% url 'inbox' %}

Do the same with static files, but they aren't named, but you drop the /static/ from them:

{% static 'up.jpg' %}
{% static 'index.html' %}

[procrasti]

Make a branch and all that, you come up with the name.