Summary:
This PR adds a stub podspec files which will be pushed to cocoapods master repo to reserve our project name on cocoapods master repo. This PR follows the suggestion given by KrauseFx in #132 132. I have reserved the name of [Flipper](https://cocoapods.org/pods/Flipper) and [FlipperKit](https://cocoapods.org/pods/FlipperKit) on cocoapods with these stub podspecs.
Pull Request resolved: https://github.com/facebook/flipper/pull/330
Reviewed By: passy
Differential Revision: D13118301
Pulled By: priteshrnandgaonkar
fbshipit-source-id: 754a69ee9577c1357cf3284b5c89143d46f69c87
