Allow user-defined temperature

Would be useful to accept a user-defined temperature for the model being used. e.g.

```
ActiveCortex::Generator.generate(
    record: self,... , temperature:
  )
```

Allows user to describe the level of "randomness" they want from GPT.
[OpenAI defaults to 1](https://platform.openai.com/docs/api-reference/chat/create#chat-create-temperature)