Fixed RAC 2.3 compatibility issues

Test passing on RAC 2.3 and RAC 2.1.8
1) Added RAC_DEBUG_SIGNAL_NAMES environment variable to TEST scheme, so RACStream -setNameWithFormat: works
2) didSubscribeWithDisposable expects RACCompoundDisposable instead of RACDisposable
Podfile.lock should be checked in to repository

http://guides.cocoapods.org/using/using-cocoapods.html#what-is-a-podfile.lock

And if you add Pods directory to repository, Pods/Manifest.lock should be added too
(I personally prefer not to add Pods dir to repository at all)
Merge branch 'add_podfile_lock'