Placeholder to use full bounds

Fixes #221

Current behavior causes placeholder to first
use full bounds at `setPlaceholder`, then use centered bounds at `onBoundsChange`, causing a broken fade in:

![http://i.imgur.com/d4yMhrf.gif](http://i.imgur.com/d4yMhrf.gif)

This reverts to previous behavior of using full bounds for placeholder:

![http://i.imgur.com/weWxfME.gif](http://i.imgur.com/weWxfME.gif)
Correct for skia decoding problem during underflow.

Adapted from http://b.android.com/6066#c12
Automatically start and stop AnimationDrawables
Merge pull request #285 from square/jw/android-bug-6066

Correct for skia decoding problem during underflow.
avoid crash when decode WebP network stream
Bugfix. only-if-cached was invalid
Merge pull request #264 from eveliotc/placeholder-bounds

Placeholder to use full bounds
Merge pull request #197 from Meituan-Android/master

Avoid crash when decode WebP network stream
Merge pull request #318 from f2prateek/animation-drawables

Automatically start and stop AnimationDrawables
Merge pull request #300 from Meituan-Android/bugfix/only_if_cached

Bugfix. only-if-cached was invalid for okhttp
Remove prefix Utils. because import static
Merge pull request #345 from tttzof351/master

Remove prefix Utils. because import static
Remove prefixes using static import
Merge pull request #347 from amatellanes/master

Remove prefixes using static import
Switch conditional to OR.
Merge pull request #350 from square/jw/or

Switch conditional to OR.
Custom transformations should throw on main thread.
Merge pull request #355 from square/dimitris/throw-to-main

Custom transformations should throw on main thread.
Update readme with proguard instructions.
Merge pull request #356 from square/dimitris/update-readme

Update readme with proguard instructions.