Exercism: "Binary Search Tree in Clojure"

I solved the Binary Search Tree problem in Clojure.

I wrote three versions of the to-list function which makes a depth-first traversal of the tree returning the sequence of visited values.

This is my first version:

This is the second one using concat:

And the last one using the tree-seq function that I discovered looking at other solutions in Exercism: You can nitpick my solutions here and/or see all the exercises I've done so far in this repository.