Combine signals
I thought this was useful, but it does make the library larger. Thoughts?
Flaky travis:
SignalsTests iOS: xctest (13908) encountered an error (Failed to load the test bundle. (Underlying error: The bundle “SignalsTests iOS” couldn’t be loaded because it is damaged or missing necessary resources. The bundle is damaged or missing necessary resources. dlopen_preflight(/Users/travis/Library/Developer/Xcode/DerivedData/Signals-hbucudalqtyounamwskaiplydfgr/Build/Products/Release-iphonesimulator/SignalsTests iOS.xctest/SignalsTests iOS): Library not loaded: /usr/lib/libauto.dylib Referenced from: /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation Reason: no suitable image found. Did find: /usr/lib/libauto.dylib: mach-o, but not built for iOS simulator)) Test session results and logs: /Users/travis/Library/Developer/Xcode/DerivedData/Signals-hbucudalqtyounamwskaiplydfgr/Logs/Test/Test-Signals iOS-2019.04.24_18-15-15-+0000.xcresult