Add go examples

Code and site changes to support the Go programming language and, specifically, Gophercloud v1.
This needs to be:

```go
snapshots.List(client).EachPage(func(page pagination.Page) (bool, error) {
	snapshots, err := snapshots.ExtractSnapshots(page)
	for _, s := range snapshots {
		// ...
	}
	return true, nil
})
```