I’m dying to have a better GitHub flavored markdown support in sublime, namely I’m looking for these:

1. Auto mark URLs as meta.link scope
2. Fenced code blocks should be marked as markup.raw.block. Even better is to enable language specific syntax highlighting for the code block
3. Multiple underscores in words should be allowed.
4. YAML Front Matter syntax highlighting for MultiMarkdown

Regexes on Mardown.tmLanguage is quite complex and horrendous! Anyone knows how to add these features?