Missing tag 1.5.1

[MaciejRz]

In FastImageCache.podspec.json you're pointing to tag 1.5.1 but there is no such tag on this repository. The outcome ot that is unpredictable (at least I have no interest in searching for it) but definitely different from expected. And it is even worse as it wrongly states 1.5.1 was installed but what you get under the hood is far from that.