Update the development version (i.e. --devel) of s3cmd to 1.5.0.alpha3

The 1.5.0 branch includes some nice additions with regards to invalidating CloudFront resources for S3 static websites. There's a nice explanation of the problem with versions prior to version 1.5.0 available [here](http://www.whatwherewhy.me/blog/2012/01/15/an-update-to-s3cmd-to-add-cloudfront-invalidation-for-s3-static-websites/) (written by @aral???).