Add go examples

Code and site changes to support the Go programming language and, specifically, Gophercloud v1.
This needs to be removed - Rackspace cloud block storage doesn't support updating snapshot metadata. Instead they support a more general update, like so:

```go
// Only Name and Description may be updated
opts := snapshots.UpdateOpts{Name: "new_name"}
s, err := snapshots.Update(client, "{snapshotId}", opts).Extract()
```