Revert "Fix parsing of unclosed Markdown delimiters."

This reverts commit a8ea6504e9.

It causes problems for colour support and it doesn't really fix the
issue in full generality. The proper fix is to include a real Markdown
parser.

matrix/colors.py

@@ -218,7 +218,7 @@ class Formatted(object):
                 text = text + line[i]
                 i = i + 1
 
-        substrings.append(FormattedString(text, DEFAULT_ATTRIBUTES.copy()))
+        substrings.append(FormattedString(text, attributes))
         return cls(substrings)
 
     @classmethod