Fixed Glacier response timestamp parsing

Some responses have a millisecond component and some do not.
Also do not attempt to parse null timestamps, duh.
Fixed Glacier archive deletion call
Added pagination support to Glacier list requests

Fixes bug where only the first 10 vaults would be returned
in a list request.
Merge pull request #55 from labisso/glacierfixes

Fixes for AWS Glacier support (2013.07)