* Downloads given application package name, version and offer type. Version
* code and offer type can be fetch by <code>details</code> interface.
**/
public InputStream download(String packageName, int versionCode, int offerType) throws IOException {
BuyResponse buyResponse = purchase(packageName, versionCode, offerType);
AndroidAppDeliveryData appDeliveryData = buyResponse.getPurchaseStatusResponse().getAppDeliveryData();
String downloadUrl = appDeliveryData.getDownloadUrl();
HttpCookie downloadAuthCookie = appDeliveryData.getDownloadAuthCookie(0);
return executeDownload(downloadUrl, downloadAuthCookie.getName() + "=" + downloadAuthCookie.getValue());