Add the Ren'Py recipe.
Update .gitignore.
Sample key, since without a valid key, things fail to initialize.
Modify the downloader and integrate it with the rest of the system.

* It looks in more places to find the obb file.
* Once the OBB is present, the downloader sends an intent to the PythonActivity.
* The PythonActivity reads the expansion file location from the intent.
* SDLSurfaceView places the expansion file location into ANDROID_EXPANSION.