Vendor folder is not synced with configuration

The committed vendor content is out sync with the configuration.

```
$ dep check
# vendor is out of sync:
github.com/flosch/pongo2: hash of vendored tree not equal to digest in Gopkg.lock
github.com/spf13/viper: hash of vendored tree not equal to digest in Gopkg.lock
github.com/yudai/gotty: hash of vendored tree not equal to digest in Gopkg.lock
```