Fix for https://github.com/jayfajardo/openlibrary/issues/16

Problem
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* Received `302` redirects when attempting to access `openlibrary.org` using this client.
* `302` are not handled in the case statements, so the response was returning `nil`

Summary of changes
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* Updated the `API_URL` for open library to use secure `https`
* Added `HANDLE_REST_CLIENT_RESPONSE` lamda to handle common response code actions
* Added a helper, `perform_get_request` for common GET request code