tests: Big push to get the tests to pass again. - Lots of fixes everywhere in the code. - Try to handle debug logging in the multiprocessing worker pool when running in pytest. Not perfect, but usable for now. - Replace all `.md` test files with `.html` since now a auto-format extension always sets the format. - Replace `out` with `outfiles` in most places since now blog archives are added to the bake output and I don't want to add expected outputs for blog archives everywhere.

---
url: /archives/2016.html
in:
    templates/_year.html: |
        Posts in {{year}}
        {% for post in pagination.posts -%}
        {{post.url}}
        {% endfor %}
    posts/2015-12-01_post0.html: ''
    posts/2016-01-01_post1.html: ''
    posts/2016-01-02_post2.html: ''
out: |
    Posts in 2016
    /2016/01/02/post2.html
    /2016/01/01/post1.html