Smart Home: Allow to set https agent options

[bramkragten]

We would like to set maxSockets and other options for the https agent, it would be nice if we could pass an agent to use:

const agent = new https.Agent({
   maxSockets: 25
});

const sh = smarthome({ jwt, agent });

It would probably also be wise to set a sane default maxSockets, as the default infinity might not be wise for an app dealing with a lot of traffic,

I can make a PR for this if accepted.

[Fleker]

FYI @proppy