GetEvents() does not support the 'unaggregated' API argument

[golliher]

It is useful to be able to search the event stream for unaggregated events.

GetEvents() does not appear to support the optional 'unaggregated' parameter documented here:

• https://docs.datadoghq.com/api/?lang=python#query-the-event-stream

[bkabrda]

Just to keep the reference here: this is being worked on in #203