Adding an iOS Unit Testing target referencing #405
added +once:
clarify docs
yo dawg I heard u like blockz
better docs
test cleanup
Merge branch 'master' into once

Conflicts:
	ReactiveCocoaFramework/ReactiveCocoaTests/RACSignalSpec.m
Merge remote-tracking branch 'KyleLeneau/ios_unit_test_target' into ios-testing-target

Conflicts:
	ReactiveCocoaFramework/ReactiveCocoa.xcodeproj/project.pbxproj
Added iOS testing target, refactored RACLifting spec.
Added iOS specific RACLifting spec.
Imported RACBacktrace private header for GCD overrides.
Extracted the NSOperationQueue RACBacktrace test.
Add iOS target tests to CI build.
Merge branch 'master' into ios-testing-target
Revert "Extracted the NSOperationQueue RACBacktrace test."

This reverts commit 708341f140352c648bb3c1e178e4dc342afa8702.
Wrapped NSOperationQueue test in platform conditional.
Reverted refactoring of RACLifting specs.
Changed the platform wrapping to mirror the others.
Moved the frameworks in the proper groups.
iOS needs to empty the pool after the dispose.