Correct the spelling of CocoaPods in README

[ReadmeCritic]

This pull requests corrects the spelling of CocoaPods 🤓 https://github.com/CocoaPods/shared_resources/tree/master/media

One day I’ll make a bot that looks through the READMEs of all Pods, looks to see if it uses “Cocoapods” and PRs “CocoaPods” :D

— Ørta (@orta) February 10, 2016