Revert "OK, no idea what is happening, reverting"

This reverts commit 1ebd8cf025.

So, this was actually correct, going with it!

pelicanconf.py

@@ -32,7 +32,17 @@ DEFAULT_PAGINATION = 100
 PLUGIN_PATHS = ['./pelican-plugins', './plugins-custom']
 PLUGINS = ['dateish', 'extract_toc', 'i18n_subsites', 'summary', 'events-ics','complex_footnotes', 'stream', 'thumbnailer']
 
-MD_EXTENSIONS = ['codehilite', 'extra', 'toc']
+MARKDOWN = {
+    'extension_configs': {
+        'markdown.extensions.codehilite': {'css_class': 'highlight'},
+        'markdown.extensions.extra': {},
+        'markdown.extensions.meta': {},
+        'markdown.extensions.toc': {
+            'marker': '[TOC]',
+        },
+    },
+    'output_format': 'html5',
+}
 
 STATIC_PATHS = ['extra/favicon.ico', 'images', 'pdfs', 'stream']
 EXTRA_PATH_METADATA = {