Switch docs to MKDocs (#602)

Fixes #601. Merged in 6f87b32 from the md3 branch and did a lot of cleanup.

Changes include:

* Removed old docs build tool, templates, etc.

* Added MkDocs config file, etc.

* filename.txt => filename.md

* pythonhost.org/Markdown => Python-Markdown.github.io

* Markdown lint and other cleanup.

* Automate pages deployment in makefile with `mkdocs gh-deploy`

    Assumes a git remote is set up named "pages". Do

        git remote add pages https://github.com/Python-Markdown/Python-Markdown.github.io.git

    ... before running `make deploy` the first time.

1 files changed, 77 insertions, 0 deletions

diff --git a/docs/extensions/sane_lists.md b/docs/extensions/sane_lists.md
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+title: Sane Lists Extension
+
+Sane Lists
+==========
+
+Summary
+-------
+
+The Sane Lists extension alters the behavior of the Markdown List syntax
+to be less surprising.
+
+This extension is included in the standard Markdown library.
+
+Syntax
+------
+
+Sane Lists do not allow the mixing of list types. In other words, an ordered
+list will not continue when an unordered list item is encountered and
+vice versa. For example:
+
+```md
+1. Ordered item 1
+2. Ordered item 2
+
+* Unordered item 1
+* Unordered item 2
+```
+
+will result in the following output:
+
+```html
+<ol>
+  <li>Ordered item 1</li>
+  <li>Ordered item 2</li>
+</ol>
+
+<ul>
+  <li>Unordered item 1</li>
+  <li>Unordered item 2</li>
+</ul>
+```
+
+Whereas the default Markdown behavior would be to generate an unordered list.
+
+Note that, unlike the default Markdown behavior, if a blank line is not
+included between list items, the different list type is ignored completely.
+This corresponds to the behavior of paragraphs. For example:
+
+```md
+A Paragraph.
+* Not a list item.
+
+1. Ordered list item.
+* Not a separate list item.
+```
+
+With this extension the above will result in the following output:
+
+```html
+<p>A Paragraph.
+* Not a list item.</p>
+
+<ol>
+  <li>Ordered list item.
+  * Not a separate list item.</li>
+</ol>
+```
+
+In all other ways, Sane Lists should behave as normal Markdown lists.
+
+Usage
+-----
+
+See [Extensions](index.md) for general extension usage, specify
+`markdown.extensions.sane_lists` as the name of the extension.
+
+This extension does not accept any special configuration options.