Kc/v1 rest api port

[KaseyCantu]

Refactoring the SDK to the v1 Spec of ShipEngine API from the JSONRPC spec that was previously implemented.

• [x] Refactor client
• [x] Refactor ShipEngine->validateAddresses() to be able to take a single address or an array of addresses.
• [ ] Refactor validateAddresses() tests.
• [ ] Refactor Tracking Services.
• [ ] Implement getRates.
• [ ] Implement createLabel.
• [ ] Implement createLabelById.