[fix] Image rendering in Safari

The use of 'max-height:100%' on the inner image can cause extremely poor
render performance in Safari. Remove the inner image and simplify
`Image` to use a single view. This fixes the following additional bugs:

Fix #202
Fix #226

examples/components/Image/ImageExample.js

@@ -652,6 +652,6 @@ var styles = StyleSheet.create({
 
 examples.forEach((example) => {
   storiesOf('component: Image', module)
-    .addDecorator((renderStory) => <View>{renderStory()}</View>)
+    .addDecorator((renderStory) => <View style={{ width: '100%' }}>{renderStory()}</View>)
     .add(example.title, () => example.render())
 })