Improvements

- Conservative dependencies versions
- Travis CI badge
- Improved README
haha! If it's confuse to you, perhaps we need to improve. I had this discussion with @mateusg about have both `Resources` and `Models` namespaces, but we end up to agree that it was not necessary and the models under our service API can whether be or not resources. The usage of `Jeckle::Resource` and `Jeckle::Model` just implies that a model could be or not a resource represented by the API we are consuming, but our class continues to be a model, you see? `Jeckle::Resource` will include things like `search`, `find`, `default_api` macro, and so on, `Jeckle::Resource` will only include `ActiveModel` and `Virtus` it's ideal to handle nested objects on the main resource, for example:

```js
// User resource
{ // /user/:id
  name: 'Brenno Costa',
  email: 'brennolncosta@gmail.com'
  profile: { // there is no such /user/profile
    description: 'Lorem Ipsum',
    favourite_color: 'blue'
  }
}
```

In this case we would have `class User; include Jeckle::Resource; end` and `class Profile; include Jeckle::Model; end`