Fix params not in alphabetical order

Beeleads isn't accepting not ordered parameter keys, for example, if I send the params in alphabetical order, it works like a charm `client.lead({'email' => 'sample@example.net', 'firstname' => 'Tiago'})`. But when I send not in alphabetical order, for example `client.lead({'firstname' => 'Tiago', 'email' => 'sample@example.net'})`, the new lead isn't accepted and returns `"response"=>{"status"=>401, "message"=>"Access Denied"}`.

EDIT:
The same problem happens when the hash value is `nil`