Remove bundled copy of python-markdown-math extension

Pull it from PyPI instead.

changelog

@@ -8,6 +8,7 @@ Incompatible changes:
 * The output now uses HTML5 instead of HTML4.
 * The custom markups are now registered with entry points.
 * The ``get_custom_markups()`` method has been removed.
+* New dependency: ``python-markdown-math``.
 
 Version 2.0.1, 2017-06-24
 =========================

markups/markdown.py

@@ -108,16 +108,16 @@ def _split_extension_config(self, extension_name):
 	def _apply_extensions(self):
 		extensions = (self.requested_extensions +
 			self.global_extensions + self.document_extensions)
-		extension_names = {"markdown.extensions.extra", "markups.mdx_mathjax"}
+		extension_names = {"markdown.extensions.extra", "mdx_math"}
 		extension_configs = {}
 
 		for extension in extensions:
 			if extension == 'mathjax':
 				mathjax_config = {"enable_dollar_delimiter": True}
-				extension_configs["markups.mdx_mathjax"] = mathjax_config
+				extension_configs["mdx_math"] = mathjax_config
 			elif extension == 'remove_extra':
 				extension_names.remove("markdown.extensions.extra")
-				extension_names.remove("markups.mdx_mathjax")
+				extension_names.remove("mdx_math")
 			else:
 				name, config = self._split_extension_config(extension)
 				if name in _canonicalized_ext_names:

setup.py

@@ -33,6 +33,7 @@
 	'author_email': 'mitya57@gmail.com',
 	'url': 'https://github.com/retext-project/pymarkups',
 	'packages': ['markups'],
+	'install_requires': 'python-markdown-math',
 	'extras_require': {
 		'Markdown': ['Markdown>=2.6'],
 		'reStructuredText': ['docutils'],