torque add torrent callback possibilities

add_torrent_callbacks.js

var request = app.btapp.get('torrent').download({
    url: 'magnet:?xt=urn:btih:D075D45EA1DA3E20BA148A08D984EFFC439273A4',
    callback: function() {
        // torrent has been added to the torrent list of the client.
        // this is called immediately on magnet links,
        // but might take a bit for http://*.torrent file urls
    }
});
request.then(function(res) {
    // the client has heard and acknowledged your request
}, function(res) {
    // awwww shit
});

request.done(function(res) {
    // I only care about success!
});

request.fail(function(res) {
    // I only care about failure!
});