~/Library/Application Support/Sublime Text 2/Packages/Ruby/Ruby.sublime-options looks like this:

{
	"tabSize":2,
	"translateTabsToSpaces":true
}

However, after restarting Sublime, I find that even when I open Ruby files, it’s defaulting to a tab size of 4 and not using soft tabs for some files, even when those files have the .rb extension.