extra options parameter to callback

hey, first of all i've never githubbed before, so be nice :P 

so what i'm doing in my app is running r2j for an array of feeds but on the frontend I want those feeds to each go into a separate div with an id that i predefine. 

so my change is to add an extra parameter to the r2j call that will be passed as an extra parameter to the callback. as far as i know it is backwards compatible so won't break any current implementations but i haven't tested it thoroughly

also, not sure how the package.json thing works on github, i assume if you do pull you will just use your own one, don't want mine to overwrite yours or anything.

anyway, have a look, i can keep using my fork but of you want the changes in your branch go ahead.