Various Javadoc improvements and corrections.
fix for case where resume is async and original is still emits events after onError
handle multiple onError calls
Merge pull request #311 from daveray/update-javadoc

Various Javadoc improvements and corrections.
Merge pull request #312 from petermd/fix-errorresumenext

Fix for OperatorOnErrorResumeNextViaObservable and async Resume