Avoided ImageLoader.getInstance() usages in the code (#158)
Extracted ImageLoaderEngine from ImageLoader.
Changed API: PauseOnScrollListener requires ImageLoader instance in
constructor
Added support of "content://", "assets://", "drawable://" schemes for
image URIs from the box. Included ExtendedImageDownloader into the
library, use it as default downloader.
Sample: Removed local ExtendedImageDownloader, use one from the library.
Use new API of PauseOnScrollListener
Sample: Use the latest lib snapshot