TRIVIAL DRIVE - SAMPLE FOR IN-APP BILLING VERSION 3
Copyright (c) 2012 Google Inc. All rights reserved.
Bruno Oliveira, 2012-11-29

This sample can't be run as-is. You have to create your own
application instance in the Developer Console and modify this
sample to point to it. Here is what you must do:

ON THE GOOGLE PLAY DEVELOPER CONSOLE:
1. Create an application on the Developer Console. You must use
   version 2, available at https://play.google.com/apps/publish/v2/
   or later. In-app billing version 3 is not available in the older
   versions of Developer Console.

2. In that app, create MANAGED in-app items with these IDs:
     premium, gas
   Set their prices to 1 dollar (or any other price you like,
   but make it a small price since this is just for testing purposes).

3. Make sure your test account (the one you will use to test purchases)
   is correctly listed in the "testing" section. Your test account CANNOT
   BE THE SAME AS THE PUBLISHER ACCOUNT. If it is, purchases won't go
   through.

4. Grab the application's public key (a base-64 string) -- you will need
   that next. Note that this is the *application's* public key, not the
   developer public key. You can find the application's public key in
   the "Services & API" page for your application.

IN THE CODE
5. Open MainActivity.java and replace the placeholder key with your app's public key.
6. Change the sample's package name to your package name
   (you can do that using your favorite IDE's refactoring feature, or manually
   by changing the code directories and package declarations in .java files)
7. Don't forget to update the package name in AndroidManifest.xml. Many refactoring
   tools fail to do that automatically!
8. Make sure that AndroidManifest.xml lists the updated package name!
9. Export an APK, signing it with your PRODUCTION (not debug) developer certificate

BACK TO GOOGLE PLAY DEVELOPER CONSOLE
10. Upload your APK to Google Play
11. Wait 2-3 hours for Google Play to process the APK (if you don't, you might
    see errors where Google Play says that "this version of the application
    is not enabled for in-app billing" or something similar)
    
TEST THE CODE
12. Install the APK, signed with your PRODUCTION certificate, to a test device [*] 
13. Run the app
14. Make purchases (make sure you're purchasing with an account that's NOT
    your developer account with which you uploaded the app to Google Play).

Remember to refund any real purchases you make, if you don't want the 
charges to actually to through.

[*]: it will be easier to use a test device that doesn't have your
developer account logged in; this is because, if you attempt to purchase
an in-app item using the same account that you used to publish the app,
the purchase will not go through.