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, 111 deletions

diff --git a/docs/extensions/meta_data.txt b/docs/extensions/meta_data.txt
deleted file mode 100644
index 4a4fe62..0000000
--- a/docs/extensions/meta_data.txt
+++ /dev/null
@@ -1,111 +0,0 @@
-title:      Meta-Data Extension
-prev_title: HeaderId Extension
-prev_url:   header_id.html
-next_title: New Line to Break Extension
-next_url:   nl2br.html
-
-Meta-Data
-=========
-
-Summary
--------
-
-The Meta-Data extension adds a syntax for defining meta-data about a document.
-It is inspired by and follows the syntax of [MultiMarkdown][]. Currently,
-this extension does not use the meta-data in any way, but simply provides it as
-a `Meta` attribute of a Markdown instance for use by other extensions or
-directly by your python code.
-
-This extension is included in the standard Markdown library.
-
-[MultiMarkdown]: http://fletcherpenney.net/MultiMarkdown_Syntax_Guide#metadata
-
-Syntax
-------
-
-Meta-data consists of a series of keywords and values defined at the beginning 
-of a markdown document like this:
-
-    Title:   My Document
-    Summary: A brief description of my document.
-    Authors: Waylan Limberg
-             John Doe
-    Date:    October 2, 2007
-    blank-value: 
-    base_url: http://example.com
-
-    This is the first paragraph of the document.
-
-The keywords are case-insensitive and may consist of letters, numbers, 
-underscores and dashes and must end with a colon. The values consist of 
-anything following the colon on the line and may even be blank.
-
-If a line is indented by 4 or more spaces, that line is assumed to be an
-additional line of the value for the previous keyword. A keyword may have as
-many lines as desired. 
-
-The first blank line ends all meta-data for the document. Therefore, the first
-line of a document must not be blank.
-
-Alternatively, You may use YAML style deliminators to mark the start and/or end
-of your meta-data. When doing so, the first line of your document must be `---`.
-The meta-data ends at the first blank line or the first line containing an end
-deliminator (either `---` or `...`), whichever comes first. Even though YAML
-deliminators are supported, meta-data is not parsed as YAML.
-
-All meta-data is stripped from the document prior to any further processing
-by Markdown.
-
-Usage
------
-
-See [Extensions](index.html) for general extension usage, specify `markdown.extensions.meta`
-as the name of the extension.
-
-Accessing the Meta-Data
------------------------
-
-The meta-data is made available as a python Dict in the `Meta` attribute of an 
-instance of the Markdown class. For example, using the above document:
-
-    >>> md = markdown.Markdown(extensions = ['markdown.extensions.meta'])
-    >>> html = md.convert(text)
-    >>> # Meta-data has been stripped from output
-    >>> print html
-    <p>This is the first paragraph of the document.</p>
-
-    >>> # View meta-data
-    >>> print md.Meta
-    {
-    'title' : ['My Document'],
-    'summary' : ['A brief description of my document.'],
-    'authors' : ['Waylan Limberg', 'John Doe'],
-    'date' : ['October 2, 2007'],
-    'blank-value' : [''],
-    'base_url' : ['http://example.com']
-    }
-
-Note that the keys are all lowercase and the values consist of a list of 
-strings where each item is one line for that key. This way, one could preserve 
-line breaks if desired. Or the items could be joined where appropriate. No 
-assumptions are made regarding the data. It is simply passed as found to the 
-`Meta` attribute.
-
-Perhaps the meta-data could be passed into a template system, or used by
-various Markdown extensions. The possibilities are left to the imagination of
-the developer.
-
-Compatible Extensions
----------------------
-
-The following extensions are currently known to work with the Meta-Data 
-extension. The keywords they are known to support are also listed.
-
-* [HeaderId](header_id.html)
-    * `header_level`
-    * `header_forceid`
-* [WikiLinks](wikilinks.html)
-    * `wiki_base_url`
-    * `wiki_end_url`
-    * `wiki_html_class`
-