Animated WebP support (#605)

* Updating to support animated WebP

* Fix a deadlock with display link

* Fix playhead issue.

* Fix up timing on iOS 10 and above

* Don't redraw the same frame over and over

* Clear out layer contents if we're an animated GIF on exit range

* Clear out cover image on exit of visible range

* Don't set cover image if we're no longer in display range.

* Don't clear out image if we're not an animated image

* Only set image if we're not already animating

* Get rid of changes to podfile

* Add CHANGELOG entry

* Update license

* Update PINRemoteImage

* Remove commented out lines in example

Texture.podspec

@@ -45,7 +45,7 @@ Pod::Spec.new do |spec|
   end
   
   spec.subspec 'PINRemoteImage' do |pin|
-      pin.dependency 'PINRemoteImage/iOS', '= 3.0.0-beta.12'
+      pin.dependency 'PINRemoteImage/iOS', '= 3.0.0-beta.13'
       pin.dependency 'PINRemoteImage/PINCache'
       pin.dependency 'Texture/Core'
   end