Handle Thrown Errors with UnsafeSubscribe

... oxymoronic commit here ... adding some safety to unsafeSubscribe.
... fixes https://github.com/Netflix/RxJava/issues/1090
Merge pull request #1091 from benjchristensen/unsafeSubscribe-error-handling

Handle Thrown Errors with UnsafeSubscribe
Reconnecting ObservableExecutionHook.onCreate

Somehow this got lost in the refactorings over the past few weeks.