Removed RACActiveSignals checking in RACDynamicSignal.
Fixed some tests.
Removed some tests that were testing implementation details.
Isolated multicasted subscription disposal test because ARC.
This isn't needed anymore.
Merge remote-tracking branch 'origin/master' into remove-racactivesignals
Merge pull request #1135 from ReactiveCocoa/remove-racactivesignals

Remove RACActiveSignals