alias for latest s3 data

[kevinkreiser]

right now we have our s3 bucket full of files with dates in their names. that is fine on one hand as long as your tool can list them and then get the newest or oldest or whatever. but it would be nice to have a redirect in place to get the newest one. apparently s3 lets you put a metadata on an object that lets you set a redirect to another place in the bucket. to make this happen we'd need to update the push_tiles.py to reset the metadata on the latest version of every given thing we push.

this leads me to wonder about a better way.. maybe we should start sticking this stuff in a folder with the date on it. then we just need a latest folder that redirects to the dated one. not sure if the redirect is more like an alias though so that different parts of the path are just synonyms for something else.