fixed one Android issue 

Fixed an issue in which the same photo would get sent to Instagram over and over even is the base64 encoding was for another photo. On some devices the photo that was first written on the filesystem, called instagram.png, would never get rewritten.

The fix creates random named photos (instagram-xxxx.png) instead of a fixed name (instagarm.png). All previously created images are deleted before a new photo is created

This is the same problem described in issue #8