Allow user to skip iTunes Connect submission after uploading IPA

This PR adds option to skip iTunes Connection app submission after uploading IPA. 

I've tried rewriting `deliver.rb`, but I'm not sure whether it's 100% OK :wink: 

Bad thing is that this is not backwards-compatible. 
When reading this, it's not clear to me: Why do I have to use a flag + ```beta_ipa```?