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, 0 insertions, 75 deletions

diff --git a/docs/extensions/admonition.txt b/docs/extensions/admonition.txt
deleted file mode 100644
index d68bd5d..0000000
--- a/docs/extensions/admonition.txt
+++ /dev/null
@@ -1,75 +0,0 @@
-title:      Admonition Extension
-prev_title: Smart Strong Extension
-prev_url:   smart_strong.html
-next_title: CodeHilite Extension
-next_url:   code_hilite.html
-
-Admonition
-==========
-
-Summary
--------
-
-The Admonition extension adds [rST-style][rST] admonitions to Markdown documents.
-
-This extension is included in the standard Markdown library.
-
-[rST]: http://docutils.sourceforge.net/docs/ref/rst/directives.html#specific-admonitions
-
-Syntax
-------
-
-Admonitions are created using the following syntax:
-
-    !!! type "optional explicit title within double quotes"
-        Any number of other indented markdown elements.
-
-        This is the second paragraph.
-
-`type` will be used as the CSS class name and as default title. It must be a
-single word. So, for instance:
-
-    !!! note
-        You should note that the title will be automatically capitalized.
-
-will render:
-
-    <div class="admonition note">
-    <p class="admonition-title">Note</p>
-    <p>You should note that the title will be automatically capitalized.</p>
-    </div>
-
-Optionally, you can use custom titles. For instance:
-
-    !!! danger "Don't try this at home"
-        ...
-
-will render:
-
-    <div class="admonition danger">
-    <p class="admonition-title">Don't try this at home</p>
-    <p>...</p>
-    </div>
-
-If you don't want a title, use a blank string `""`:
-
-    !!! important ""
-        This is a admonition box without a title.
-
-results in:
-
-    <div class="admonition important">
-    <p>This is a admonition box without a title.</p>
-    </div>
-
-
-rST suggests the following `types`, but you're free to use whatever you want:
-    attention, caution, danger, error, hint, important, note, tip, warning.
-
-Styling
--------
-
-There is no CSS included as part of this extension. Look up the default
-[Sphinx][sphinx] theme if you need inspiration.
-
-[sphinx]: http://sphinx.pocoo.org/