Efficiently obtain subtree for interval-tree

[FiV0]

Hey, I was wondering if the current implementation would permit to get extended to efficiently obtain a subtree. Something along the lines of

(def x (dean/interval-map {[1 3] :x1
                           [4 7] :x2
                           [8 9] :x3
                           [0 5] :x4
                           [6 8] :x5
                           [9 9] :x6
                           [3 9] :x7
                           [4 5] :x8}))

(dean/subtree x [5 5]) ; => {[4 7] :x2 [0 5] :x4 [3 9] :x7 [4 5] :x8}

by efficient I mean at the order of log(n), where n is the number of intervals in the original tree.