change source option of make to be an object of arbitrary more info

use case is embedding a json object into the 'thing' attribute of info (http://htmlpreview.github.io/?https://github.com/derrickoswald/thing-tracker-network/blob/master/thingmaker/docs/modules/make_torrent.html), so i thought it might make more sense to generalize from only allowing an extra source attribute to allowing arbitrary more attributes.

let me know what you think and if there is something i need to do for this to be accepted