coinbase.go
func (c Client) GetContacts(params *ContactsParams) (*contactsHolder, error) {
	holder := contactsHolder{}
	if err := c.Get("contacts", params, &holder); err != nil {
		return nil, err
	}
	for _, contact := range holder.Contacts {
		if contact.Contact.Email != "" {
			holder.Emails = append(holder.Emails, contact.Contact.Email)
		}
	}
	return &holder, nil
}
func (c Client) GetContacts(params *ContactsParams) (*contactsHolder, error) {
	holder := contactsHolder{}
	if err := c.Get("contacts", params, &holder); err != nil {
		return nil, err
	}
	for _, contact := range holder.Contacts {
		if contact.Contact.Email != "" {
			holder.Emails = append(holder.Emails, contact.Contact.Email)
		}
	}
	return &holder, nil
}
// GetContacts gets a users contacts