Beta 2 - Serialization and Rate Limiting

Prototype serialization with the verify object:

• Some conflicts when allowing $_SESSION to auto serialize
• Since verification entity is client aware, perhaps should use the client to serialize.

Retry Rate Limited Messages

• Not configurable, should get config from main client, and allow override
• Like: $client->message(['config' => 'setting'])->send($message)
• Need to test that retry backs off correctly.