Back to working order

There have been API changes on the bitly front, and also some Clojure changes (declaration of dynamic vars), which together causes the clojure-bitly wrapper to be not operational at this moment. 

I forked your repo and put everything in working order, and did some changes too. 
I only focused on the parts of the API that interests me, so it's not really a full API wrapper ready for public consumption.
Documentation needs to be updated, too.