Support iterating over multiple pages of response unless disabled

[JohnPeacockMessageSystems]

If more records from an API call are returned that would fit into the default count (20), the API will include an additional header:

X-Circonus-More-Items: true

It would be really excellent if the Python API would support fetching all records automatically, either as a default option that could be disabled if that wasn't helpful, or an option to enable that behavior.

Due to a bug in the new API code, the /maintenance endpoint is currently returning expired windows, against the documented behavior, and if any given host has too many records to fit into the limited 20 count, you might not get any unexpired windows.