Fix a case where content under admonitions weren't dettabbed properly

[facelessuser]

Admonitions would not render the following case properly:

!!! note "Admonition"
    - Parent 1

        - Child 1
        - Child 2

But would render this properly:

!!! note "Admontion"
    - Parent 1
        - Child 1
        - Child 2

The problem stemmed from bad detabbing of the content, where in the first example, the child list was parsed like this:

  - Child 1
      - Child 2

This pull addresses the issue of ensuring that each block is processed properly so that content that is highly sensitive to indentation works correctly.

[facelessuser]

I'm ignoring the "checklinks" failure. I feel that should be fixed in a separate issue.

[waylan]

I think you have an error in your first example. As is, it renders to

<div class="admonition note">
<p class="admonition-title">Admonition</p>
</div>
<ul>
<li>
<p>Parent 1</p>
<ul>
<li>Child 1</li>
<li>Child 2</li>
</ul>
</li>
</ul>

.. which is correct, The - Parent 1 line is not indented by four spaces and is therefore not a child of the admonition. Therefore it gets parsed as a list outside of the admonition as it should.

However, if you use proper indentation, like this:

!!! note "Admonition"
    - Parent 1

        - Child 1
        - Child 2

Then we get the rather strange output:

<div class="admonition note">
<p class="admonition-title">Admonition</p>
<ul>
<li>
<p>Parent 1</p>
<ul>
<li>Child 1<ul>
<li>Child 2</li>
</ul>
</li>
</ul>
</li>
</ul>
</div>

And yes that is a bug which needs fixing. So, thank you.

[facelessuser]

Sorry, that was a formatting issue for the comment, not the actual test or failure.

[facelessuser]

I've corrected the comment in the pull, but the issue is valid.