S3 - GetURL returns path if Endpoint set

[linchpinstudios]

This seems like unexpected behavior but I wanted to make sure.

It appears as though if the Endpoint is set or the ACL is set to a BucketCannedACLPrivate or s3.BucketCannedACLAuthenticatedRead the interface will return the path that was passed in.

Storage.GetURL(obj.Src) // returns obj.Src

Expected behavior:

If Endpoint is set it would return {Endpoint}{path} or if there is no endpoint and public ACL it would return the standard URL for the S3 bucket Region.

I'd be happy to make a pull request for this functionality, but I would like to make sure this is the expected behavior.