code: function treeGet (address, tree) {
    return address.reduce((accum, val) => {
      return checkType(NODE, accum) ? accum.children[val] : accum[val]
    }, tree)
  }
docs: Get the value in a tree.
  @param {Array} address -
  @param {Object} tree -
  @return {*} - The value at the given address.