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)
Merge pull request #264 from eveliotc/placeholder-bounds

Placeholder to use full bounds