Add go examples

Code and site changes to support the Go programming language and, specifically, Gophercloud v1.
You also need to add the import here:

```go
import "github.com/rackspace/gophercloud/rackspace/blockstorage/v1/snapshots"

// VolumeID is required
opts := snapshots.CreateOpts{VolumeID: "foo", Name: "bar"}
```