certificate missing for s3.amazonaws.com

Hi gem cutters!

Either I get wiretapped or the ssl_certs directory doesn't contain the right certificate for s3.amazonaws.com. This problem is really hard to discover since the certificate store also contains the system certs and the rubygems version bundled with ruby comes with a ton of additional certificates. Anyway, I added a test case which checks that the included certificates are sufficient to reach the three hosts currently used by rubygems. Please verify my findings and add the missing certificate.

Thank you
Hannes