Add support for custom actions

[victor-am]

Description

This PR adds support for custom actions (like blog_posts/1/publish, and etc). The interface I thought for now was something like:

const publish = { action: 'publish', on: 'member', method: 'get' }
api.do(publish, 'blog_posts', { id: 1 })

Closes #3

[sourcelevel-bot[bot]]

Ebert has finished reviewing this Pull Request and has found:

• 4 possible new issues (including those that may have been commented here).
• 2 fixed issues! 🎉

You can see more details about this review at https://ebertapp.io/github/victor-am/rails-ranger/pulls/8.

[victor-am]

Closed until further consideration on a more pleasant API