Fixes #196

Return InvalidAppMaster if Class.forName fails. This message will be stored in the AppManager.appMasterRegistry and returned to the client when the client issues a ShutdownApplication(appId) so the client knows why the appmaster failed. Note we need to account for some sort of history server so an audit log exists similar to YARN's history manager and tracks all appmasters execution. This will be addressed is a subsequent issue opened.
Also upgraded akka to 2.3.8 which removes some bogus disassociated messages.

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Either processing results in one more logic branch. Original code still needed to do a match on Some, None. If we push this failure into AppMasterInfo, we will still need to branch there to get the failure state. Just logging the failures won't allow this state to be propagated back to the client or the REST interface which is why we need to register the state in appMasterRegistry (see prior notes to Tianlun in this PR). We probably could refactor in the future to hold various states in the appMasterRegistry eg RUNNING, FINISHED, FAILED, etc. We could do this by having a common high level State trait.