optimize docs for yard

[wenzowski]

Textile docs must have the YARD tag #@encoding utf-8 to be rendered correctly (US-ASCII default).
Links to other files can be generated with {file:Name.textile}.

Unfortunately, github doesn't know what either of these syntaxes mean so they look funny over here.

[wenzowski]

The yard tag is only required with RedCloth, which hasn't been updated in almost a year.

I've never encountered the need for this when using markdown via redcarpet.

If you'd consider using markdown, I'm happy to do a pandoc #{file}.textile -o #{file}.markdown to existing docs and sanitize results.