Update Agent to use BaseModel classes to...
Update Agent to use BaseModel classes to...

represent Agent.role & Agent.phone_numbers fields

This will enable attribute access semantics for these fields

i.e.
> agent = client.agent.get(1234)
> agent.role['id']
> agent.phone_numbers[0]['number']

> agent.role.id
> agent.phone_numbers[0].number

gadventures/gapipy