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, 33 insertions, 22 deletions

diff --git a/README.md b/README.md
index 5e8dc84..33b4f71 100644
--- a/README.md
+++ b/README.md
@@ -1,45 +1,56 @@
 [Python-Markdown][]
 ===================
 
-[![Build Status](http://img.shields.io/travis/Python-Markdown/markdown.svg)](https://travis-ci.org/Python-Markdown/markdown)
-[![Coverage Status](https://codecov.io/gh/Python-Markdown/markdown/branch/master/graph/badge.svg)](https://codecov.io/gh/Python-Markdown/markdown)
-[![Latest Version](http://img.shields.io/pypi/v/Markdown.svg)](http://pypi.python.org/pypi/Markdown)
-[![Python Versions](http://img.shields.io/pypi/pyversions/Markdown.svg)](http://pypi.python.org/pypi/Markdown)
-[![BSD License](http://img.shields.io/badge/license-BSD-yellow.svg)](http://opensource.org/licenses/BSD-3-Clause)
-[![Code of Conduct](https://img.shields.io/badge/code%20of%20conduct-contributor%20covenant-green.svg?style=flat-square)][Code of Conduct]
-
-This is a Python implementation of John Gruber's [Markdown][]. 
+[![Build Status][travis-button]][travis]
+[![Coverage Status][codecov-button]][codecov]
+[![Latest Version][mdversion-button]][md-pypi]
+[![Python Versions][pyversion-button]][md-pypi]
+[![BSD License][bsdlicense-button]][bsdlicense]
+[![Code of Conduct][codeofconduct-button]][Code of Conduct]
+
+[travis-button]: http://img.shields.io/travis/Python-Markdown/markdown.svg
+[travis]: https://travis-ci.org/Python-Markdown/markdown
+[codecov-button]: https://codecov.io/gh/Python-Markdown/markdown/branch/master/graph/badge.svg
+[codecov]: https://codecov.io/gh/Python-Markdown/markdown
+[mdversion-button]: http://img.shields.io/pypi/v/Markdown.svg
+[md-pypi]: http://pypi.python.org/pypi/Markdown
+[pyversion-button]: http://img.shields.io/pypi/pyversions/Markdown.svg
+[bsdlicense-button]: http://img.shields.io/badge/license-BSD-yellow.svg
+[bsdlicense]: http://opensource.org/licenses/BSD-3-Clause
+[codeofconduct-button]: https://img.shields.io/badge/code%20of%20conduct-contributor%20covenant-green.svg?style=flat-square
+[Code of Conduct]: https://github.com/Python-Markdown/markdown/blob/master/CODE_OF_CONDUCT.md
+
+This is a Python implementation of John Gruber's [Markdown][].
 It is almost completely compliant with the reference implementation,
-though there are a few known issues. See [Features][] for information 
-on what exactly is supported and what is not. Additional features are 
+though there are a few known issues. See [Features][] for information
+on what exactly is supported and what is not. Additional features are
 supported by the [Available Extensions][].
 
-[Python-Markdown]: https://pythonhosted.org/Markdown/
+[Python-Markdown]: https://Python-Markdown.github.io/
 [Markdown]: http://daringfireball.net/projects/markdown/
-[Features]: https://pythonhosted.org/Markdown/index.html#Features
-[Available Extensions]: https://pythonhosted.org/Markdown/extensions/index.html
-
+[Features]: https://Python-Markdown.github.io#Features
+[Available Extensions]: https://Python-Markdown.github.io/extensions
 
 Documentation
 -------------
 
 Installation and usage documentation is available in the `docs/` directory
-of the distribution and on the project website at 
-<https://pythonhosted.org/Markdown/>.
+of the distribution and on the project website at
+<https://Python-Markdown.github.io/>.
 
-See the change log at <https://pythonhosted.org/Markdown/change_log.html>.
+See the change log at <https://Python-Markdown.github.io/change_log>.
 
 Support
 -------
 
-You may ask for help and discuss various other issues on the [mailing list][] and report bugs on the [bug tracker][].
+You may ask for help and discuss various other issues on the [mailing list][]
+and report bugs on the [bug tracker][].
 
 [mailing list]: http://lists.sourceforge.net/lists/listinfo/python-markdown-discuss
-[bug tracker]: http://github.com/Python-Markdown/markdown/issues 
+[bug tracker]: http://github.com/Python-Markdown/markdown/issues
 
 Code of Conduct
 ---------------
 
-Everyone interacting in the Python-Markdown project's codebases, issue trackers, and mailing lists is expected to follow the [Code of Conduct].
-
-[Code of Conduct]: https://github.com/Python-Markdown/markdown/blob/master/CODE_OF_CONDUCT.md
+Everyone interacting in the Python-Markdown project's codebases, issue trackers,
+and mailing lists is expected to follow the [Code of Conduct].