additional params in GET request

eg
https://keen.io/docs/api/?javascript#inspect-all-collections

```javascript
client
  .get({
    url: client.url('events'),
    api_key: client.readKey(),
    include_schema: false
  })
  .then(res => {
    // Handle response
  })
  .catch(err => {
    // Handle error
  });
```

the code above doesn't work as expected -`include_schema` is not included in the request.