Gif Support

[Hatzen]

It seems when using a gif with glide we cannot open the zoom view as it crashes.
It would be nice to have animated gifs supported as well. It looks like we need to replace BitmapDrawable with more generic class, which probably leads to problems with other features like saving the image and encoding it as base64.

java.lang.ClassCastException: com.bumptech.glide.load.resource.gif.GifDrawable cannot be cast to android.graphics.drawable.BitmapDrawable
                                         at ozaydin.serkan.com.image_zoom_view.ImageViewZoom.getBitmap(ImageViewZoom.java:75)
                                         at ozaydin.serkan.com.image_zoom_view.ImageViewZoom.onClick(ImageViewZoom.java:132)
                                         at android.view.View.performClick(View.java:7125)
                                         at android.view.View.performClickInternal(View.java:7102)
                                         at android.view.View.access$3500(View.java:801)

Tested with Version 1.4.0