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, 85 insertions, 0 deletions

diff --git a/docs/change_log/release-2.3.md b/docs/change_log/release-2.3.md
new file mode 100644
index 0000000..fc1809e
--- /dev/null
+++ b/docs/change_log/release-2.3.md
@@ -0,0 +1,85 @@
+title: Release Notes for v2.3
+
+Python-Markdown 2.3 Release Notes
+=================================
+
+We are pleased to release Python-Markdown 2.3 which adds one new extension,
+removes a few old (obsolete) extensions, and now runs on both Python 2 and
+Python 3 without running the 2to3 conversion tool. See the list of changes
+below for details.
+
+Python-Markdown supports Python versions 2.6, 2.7, 3.1, 3.2, and 3.3.
+
+Backwards-incompatible Changes
+------------------------------
+
+* Support has been dropped for Python 2.5. No guarantees are made that the
+  library will work in any version of Python lower than 2.6. As all supported
+  Python versions include the ElementTree library, Python-Markdown will no
+  longer try to import a third-party installation of ElementTree.
+
+* All classes are now "new-style" classes. In other words, all classes subclass
+  from 'object'. While this is not likely to affect most users, extension
+  authors may need to make a few minor adjustments to their code.
+
+* "safe_mode" has been further restricted. Markdown formatted links must be of a
+  known white-listed scheme when in "safe_mode" or the URL is discarded. The
+  white-listed schemes are: 'HTTP', 'HTTPS', 'FTP', 'FTPS', 'MAILTO', and
+  'news'. Schemeless URLs are also permitted, but are checked in other ways - as
+  they have been for some time.
+
+* The ids assigned to footnotes now contain a dash (`-`) rather than a colon
+  (`:`) when `output_format` it set to `"html5"` or `"xhtml5"`. If you are
+  making reference to those ids in your JavaScript or CSS and using the HTML5
+  output, you will need to update your code accordingly. No changes are
+  necessary if you are outputting XHTML (the default) or HTML4.
+
+* The `force_linenos` configuration setting of the CodeHilite extension has been
+  marked as **Pending Deprecation** and a new setting `linenums` has been added
+  to replace it. See documentation for the [CodeHilite Extension] for an
+  explanation of the new `linenums` setting. The new setting will honor the old
+  `force_linenos` if it is set, but it will raise a `PendingDeprecationWarning`
+  and will likely be removed in a future version of Python-Markdown.
+
+[CodeHilite Extension]: ../extensions/code_hilite.md
+
+* The "RSS" extension has been removed and no longer ships with Python-Markdown.
+  If you would like to continue using the extension (not recommended), it is
+  archived on [GitHub](https://gist.github.com/waylan/4773365).
+
+* The "HTML Tidy" Extension has been removed and no longer ships with
+  Python-Markdown. If you would like to continue using the extension (not
+  recommended), it is archived on
+  [GitHub](https://gist.github.com/waylan/5152650). Note that the underlying
+  library, uTidylib, is not Python 3 compatible. Instead, it is recommended that
+  the newer [PyTidyLib] (version 0.2.2+ for Python 3 comparability - install
+  from GitHub not PyPI) be used. As the API for that library is rather simple,
+  it is recommended that the output of Markdown be wrapped in a call to
+  PyTidyLib rather than using an extension (for example:
+  `tidylib.tidy_fragment(markdown.markdown(source), options={...})`).
+
+[PyTidyLib]: http://countergram.com/open-source/pytidylib
+
+What's New in Python-Markdown 2.3
+---------------------------------
+
+* The entire code base now universally runs in Python 2 and Python 3 without any
+  need for running the 2to3 conversion tool. This not only simplifies testing,
+  but by using Unicode_literals, results in more consistent behavior across
+  Python versions. Additionally, the relative imports (made possible in Python 2
+  via absolute_import) allows the entire library to more easily be embedded in a
+  sub-directory of another project. The various files within the library will
+  still import each other properly even though 'markdown' may not be in Python's
+  root namespace.
+
+* The [Admonition Extension] has been added, which implements [rST-style][rST]
+  admonitions in the Markdown syntax. However, be warned that this extension is
+  experimental and the syntax and behavior is still subject to change. Please
+  try it out and report bugs and/or improvements.
+
+[Admonition Extension]: ../extensions/admonition.md
+[rST]: http://docutils.sourceforge.net/docs/ref/rst/directives.html#specific-admonitions
+
+* Various bug fixes have been made. See the [commit
+  log](https://github.com/Python-Markdown/markdown/commits/master) for a
+  complete history of the changes.