Scheduler.Inner -> Scheduler.Worker

As per decision at https://github.com/Netflix/RxJava/issues/997#issuecomment-40998613
Merge pull request #1072 from benjchristensen/scheduler.worker

Scheduler.Inner -> Scheduler.Worker
[Gradle Release Plugin] - pre tag commit:  '0.18.0'.
[Gradle Release Plugin] - new version commit:  '0.18.1-SNAPSHOT'.
0.18.0