proxy s3 connections

@drsnyder 
Using a forked version of clj-aws-s3 in the wikia group of clojars. This is temporary, since the current version (0.3.9) does not support proxy connections, which we need for connecting to our dfs cluster. This is enabled in the master branch, though, which is where I created our jar from. I left a comment to the author asking for an update (https://github.com/weavejester/clj-aws-s3/issues/55)