Blog Post: SDWebImage and Snapshot Testing

[orta]

Mix - https://artsy.slack.com/archives/gmv-ios-dev/p1461238091000264 with hints of artsy/eigen#1445

And we've got another useful blog post about ways to do better image caching

[orta]

Shipped an example repo: https://github.com/orta/ImageCachingExamples

Can pull code snippets from that, and give a script at the start to run alongside.