FFImageLoading 2.1.5

Complete history of changes available here: v2.1.3...v2.1.5

• This release fixes some stability issues from 2.1.1, 2.1.2 and 2.1.3.
• It also disables by default the fading effect when loading an image from memory cache. This behaviour can be changed by passing Configuration.FadeAnimationForCachedImages=true into ImageService.Instance.Initialize
• Preloading is now available in PCLs. Example: ImageService.Instance.LoadUrl(urlToImage).Preload();