0.34 rc

Supersedes https://github.com/CocoaPods/CocoaPods/pull/1143 

Sister: https://github.com/CocoaPods/Core/pull/160
This is by design... very few users need to have different Pod versions in a single installation and those are better served by having different installations... Supporting that on the other hand would be a huge headache for CP users (immagine wondering why the Pods in the tests have a different version that the ones in the main target).

I will always oppose to this.