Replace element struct with Element record

[semperos]

If the element struct map has remained for backwards compatibility, then I'd understand ignoring this pull request. I've encountered some issues where libraries I use sometimes try to dissoc a core field on an Enlive element, which obviously causes an error using the struct map (where it simply "downgrades" a record to a normal map).

Attached is a simple transformation from using a struct map to using a Clojure record instead. Thanks for the consideration.

[jackrusher]

This would be an improvement.