[TxMt] Twiki Bundle patch

It is a bug that words surround by underscores in snake_case_words in a TextMate Twiki document are italicized. (In this example, the word "case" is italicized.) When displayed in TWiki, those words are not italicized.

I made a small change to the Twiki language (in the Twiki bundle) to correct this--see the 'markup.italic.twiki' match in the attached patch. While I was in there, I made the same change to the 'markup.bold.twiki' match. But I intentionally didn't change the 'markup.raw.fixed.twiki' match, since I don't think it's likely that someone will type a word with a pair of '=' embedded in it. Let me know if you think I should resubmit the patch with this change (or other changes) included.

-- Daryl