circleci.go
func (c *Client) AddHerokuKey(key string) error {
	body := struct {
		APIKey string `json:"apikey"`
	}{APIKey: key}

	return c.request("POST", "/user/heroku-key", nil, nil, body)
}
func (c *Client) AddHerokuKey(key string) error {
	body := struct {
		APIKey string `json:"apikey"`
	}{APIKey: key}

	return c.request("POST", "/user/heroku-key", nil, nil, body)
}
// AddHerokuKey associates a Heroku key with the user's API token to allow
// CircleCI to deploy to Heroku on your behalf
//
// The API token being used must be a user API token
//
// NOTE: It doesn't look like there is currently a way to dissaccociate your
// Heroku key, so use with care