added support for symbols

[wildwestrom]

I currently use tailwind as a js library and it has no support for using strings.
Because of this, I decided to add support for this functionality so I can use girouette as a drop-in replacement for tailwind in my clojurescript projects.

;; You can now write
[:tag {:class '[class-name another-class-name]} "content"]
;; As opposed to just
[:tag {:class '["class-name another-class-name"]} "content"]
;; Or
[:tag.class-name.another-class-name "content"]