enable apps to extend comment.html and form.html

[ahoho]

Now apps can extend the comment and form html used by fluent_comments.

For example, in some hypothetical Django project where we have fluent_comments installed, we can have the following setup:

/project
  /app
    /templates
      /comments
        comment.html

Then, in comment.html

{% extends 'comments/comment.html' %}
{% block fluent_comment %}
{{ block.super }}
<-- New HTML here -->
{% endblock %}

[codecov-io]

Current coverage is 70.31% (diff: 100%)

Merging #87 into master will not change coverage

@@             master        #87   diff @@
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  Lines           438        438          
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  Hits            308        308          
  Misses          130        130          
  Partials          0          0          

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[vdboor]

Thanks for the pull request! I've merged it in a slightly different way, with more generic block names. (023a7a585aa05cb46c98dcb1287062b1d67d245a). I never thought of inheriting templates like this but it makes total sense to me.

I've also have another improvement waiting, which will add the same logic to our comments/comment.html template!

[ahoho]

Fantastic, thank you!