fixed the way the converter is chosen for tags with names containing symbols not suitable for python def

html tags may contain symbols like `:` and `-` which are not suitable for the python function names
simple name converter allows usage of the methods for tags like `tag:subtag-name`

Author: Fess-AKA-DeadMonk

markdownify/__init__.py

@@ -151,7 +151,8 @@ def is_nested_node(el):
                 text += self.process_tag(el, convert_children_as_inline)
 
         if not children_only:
-            convert_fn = getattr(self, 'convert_%s' % node.name, None)
+            fn_name = 'convert_%s' % node.name.translate(''.maketrans(':-', '__'))
+            convert_fn = getattr(self, fn_name, None)
             if convert_fn and self.should_convert_tag(node.name):
                 text = convert_fn(node, text, convert_as_inline)