Clarify when -do… blocks are run
Deprecate -initially:

The ordering is too confusing. Recommend that people use +defer: or
+createSignal: instead.
Rename -finally: to -doFinished:

This is hopefully less ambiguous with -doDisposed:.
Add -doSubscribed: to simplify some +createSignal: uses
Update tests for -doSubscribed: and -doFinished:
Merge branch 'replace-commands-with-actions' into deprecate-sequences

Conflicts:
	ReactiveCocoaFramework/ReactiveCocoa/RACSignal+Operations.h
	ReactiveCocoaFramework/ReactiveCocoa/RACSignal+Operations.m