Skip pstree until download url is fixed

See https://github.com/Homebrew/homebrew/pull/35135
Bump cookbooks for node['sprout']['user'] changes

Replace node['current_user'] with node['sprout']['user']

In Chef 12 node['current_user'] is root under sudo, we want this to be the normal user (e.g. pivotal) so we're using ENV['SUDO_USER'] instead. Several recipes that manage file permissions rely on this.

See https://github.com/pivotal-sprout/sprout-base/issues/3 for more info