[SVN] r3822 (Markdown)

[Charilaos Skiadas]

Enhanced Bold - Italic commands, to make them "toggleable", and to work with no selection as well. Now you can even toggle a bold selection to an italic selection and vice versa.
I kept the old snippets around just in case. They should be removed after some testing.

Changed:
A   trunk/Bundles/Markdown.tmbundle/Commands/Bold.tmCommand
A   trunk/Bundles/Markdown.tmbundle/Commands/Italic.tmCommand