Fixes #181

Improves #172.

Fixes #162

Fixes #170.

Fixes #107

Fixes #112.

Fixes #167

Source: http://java2s.com/Code/Java/2D-Graphics-GUI/AnimatedGifEncoder.htm

Fixes #161.

Fixes #155.

This only affects the default decode path where
either a GIF or a Bitmap is an acceptable 
result. The GIF only path will still return 
GifDrawables for single frame GIFs.

Fixes #160.

Fixes #159.

Fixes #158

Fixes #157

Fixes #156

Fixes #149

Fixes #148

Fixes #130.

Fixes #142.