Golint: Tsuru API

lint suggested 

```
lucasgomide/snitch/tsuru/api.go:13:6: type name will be used as tsuru.TsuruAPI by other packages, and that stutters; consider calling this API
lucasgomide/snitch/tsuru/api.go:13: warning: exported type TsuruAPI should have comment or be unexported (golint)
```