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, 35 insertions, 0 deletions

diff --git a/docs/extensions/nl2br.md b/docs/extensions/nl2br.md
new file mode 100644
index 0000000..4f5e611
--- /dev/null
+++ b/docs/extensions/nl2br.md
@@ -0,0 +1,35 @@
+title: New Line to Break Extension
+
+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
+-------
+
+```pycon
+>>> 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.md) for general extension usage, specify
+`markdown.extensions.nl2br` as the name of the extension.
+
+This extension does not accept any special configuration options.