Add OSX wheel generation instructions and upload script

Maybe note that this takes 15-20 minutes.

The files in the rackspace container may not update immediately.  I think the current longest time before they update (time to live = TTL) is 15 minutes.  New files should arrive at once though, so this would only be a problem if you are updating files with the same names: 

http://www.rackspace.com/knowledge_center/frequently-asked-question/what-is-the-ttl-attribute-in-a-cloud-files-container