Revert "Merge pull request #1542 from CocoaPods/remove_unsuported_requirements"

This reverts commit 3580763ce17ab6c91ed39725ab9580af9767aa0d, reversing
changes made to 45c695aac84cdd98b3005c5835085d27eedfd743.
Merge pull request #1544 from CocoaPods/rever_pull_request_1542

Revert "Merge pull request #1542 from CocoaPods/remove_unsuported_requir...