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, 37 deletions

diff --git a/docs/extensions/nl2br.txt b/docs/extensions/nl2br.txt
deleted file mode 100644
index 8ba27c8..0000000
--- a/docs/extensions/nl2br.txt
+++ /dev/null
@@ -1,37 +0,0 @@
-title:      New Line to Break Extension
-prev_title: Meta-Data Extension
-prev_url:   meta_data.html
-next_title: Sane Lists Extension
-next_url:   sane_lists.html
-
-New-Line-to-Break Extension
-===========================
-
-Summary
--------
-
-The New-Line-to-Break (`nl2b`) Extension will cause newlines to be treated as hard breaks; like
-StackOverflow and [GitHub][] flavored Markdown do.
-
-[Github]: http://github.github.com/github-flavored-markdown/
-
-Example
--------
-
-    >>> import markdown
-    >>> text = """
-    ... Line 1
-    ... Line 2
-    ... """
-    >>> html = markdown.markdown(text, extensions=['markdown.extensions.nl2br'])
-    >>> print html
-    <p>Line 1<br />
-    Line 2</p>
-
-Usage
------
-
-See [Extensions](index.html) for general extension usage, specify `markdown.extensions.nl2br`
-as the name of the extension.
-
-This extension does not accept any special configuration options.