Fix multiple IDAT chunks regression;
Treat chunk sizes separately rather than comparing summary sizes of all data chunks
Update changelog
0.1.3: Fix incorrect chunk size is written
Add test image.
Test includes apng support, multiple chunks per frame, crc and apng index recalculating.
crc32crypto.js: fix a few JSHint warnings
zopfli-png.js: Fix typo.
zopfli-png.js: remove unused variable.