[Command] Remove deprecated pod push
Merge pull request #2469 from CocoaPods/fabio/remove-pod-push

[Command] Remove deprecated pod push
[gemspec] Bump xcodeproj to 0.19.3

Fixes #2631.
[Analyzer] Ensure external sources are downloaded when needed

Closes https://github.com/CocoaPods/CocoaPods/issues/2494.