Pass/Define space attribute

[avocadowastaken]

It's impossible to change space value in JSON.stringify method,

It's just hardcoded

var SPACE = 2;

module.exports = function serialize(obj) {
    /* ... */
    str = JSON.stringify(obj, function (key, value) {
    /* ... */
    }, SPACE);

[ericf]

We're having that discussion in #7. Feel free to add your comments to that thread as to why you want this feature. Thanks!