Please update to v3.1 of createsend api

[andynagai]

Can you please update the module to go to the new version of the campaign monitor api?

https://api.createsend.com/api/v3.1

Your module is currently pointing to

https://api.createsend.com/api/v3

[devanshug]

Though the package doesn't directly points to v3, this could be a way to use v3.1
let client = new createsend({apiKey: api_key});

client.get(path, qs, params, callback, true)
client.post(path, qs, params, callback, true)
client.put(path, qs, params, callback, true)
client.delete(path, qs, params, callback, true)

I am not justifying this as correct, the package must use v3.1 as the default api endpoint, otherwise all the methods provided become useless.