FEATURE: Make it possible for shortcode to emit span instead of i elements

[mlwilkerson]

The question was raised in the support forum as to whether the plugin could emit <span> tags instead of <i> tags.

[mlwilkerson]

See also this blog post which makes the case, basically, that <i> tags are not the problem for accessibility that is sometimes perceived by some accessibility reporting tools. It still seems to me that it would be good to provide this option in the plugin, but it's probably more to satisfy a perception about a concern that isn't actually a problem. In other words, the problem it would solve is not an accessibility problem, but a problem with perception about accessibility. Still, that seems like a good enough reason to add this.