Update chunky_png gem 1.2.7 -> 1.2.9
Update chunky_png gem 1.2.7 -> 1.2.9

Changes can be found at:

  https://github.com/wvanbergen/chunky_png/compare/75991045aa3f29b0c7addc4974fb4ab24d3d4efd...412ab72798eb628aba9339d7a5869ca7eac986be

diffux/diffux,kalw/diffux,diffux/diffux,kalw/diffux,kalw/diffux,diffux/diffux