[MlMt] strikethrough

[Randall Gellens]

I resort to extracting the text into Word, editing there with change 
tracking enabled, then sending the Word document.  I've given up on 
Markdown in MailMate because most of the time what gets displayed in the 
preview doesn't match what I thought I was doing (e.g., italics preview 
as bold), and the copy of the message I get often doesn't look like the 
preview, so I can't rely on anything.

--Randall