Missing Gist features

[MaxLeiter]

Not all of these should be or need to be met, but I figure it may be helpful to see them listed here. Anything struck through is not currently being planned.

• ability to specify spaces/tabs, indent size, and line wrapping behavior
• embeddable files
• post editing (you can make a copy, and I'm open to being able to edit descriptions so you can add a link)
• revision history view (as we have no git backing, we would just walk up the parent attribute that Posts have)
• search all users gists