Because of too many references to bitmaps and views, it occurs out of memory exception.
I removed two arrays and used LRUCache and down-scale decoder for bitmaps.
Although it is more robust than before, it is just a rough solution.
Merge pull request #25 from dalinaum/fix-oom

fix #24 : out of memory.
Change Version Code

for Updating Google Play
fix #13 java.lang.IllegalStateException
If adapter's data is modified by non-UI threads while UI thread is traversing views,
IllegalStateException exception occurs.
This work-around uses handler.post method to avoid this exception.
Merge pull request #26 from dalinaum/fix-illegalstate

fix #13 java.lang.IllegalStateException