docs: function tree (dir, opts, cb) {
    var i = 0
    findPackage(dir, function (err, pkg) {
      pull(
        pull.depthFirst(pkg, function (pkg) {
          pkg.tree = {}
          return pull(
            pfs.readdir(path.resolve(pkg.path, 'node_modules')),
            paramap(maybe(readPackage)),
            pull.filter(function (_pkg) {
              if(!_pkg) return
              _pkg.parent = pkg
              
              pkg.tree[_pkg.name] = _pkg
              return pkg
            })
          )
        }),
        opts.post ? paramap(function (data, cb) {
          //run a post install-style hook.
          opts.post(data, cb)
        }) : pull.through(),
        pull.drain(null, function (err) {
          cb(err === true ? null : err, clean(pkg))
        })
      )
    })
  }